저염 오이지의 염분농도와 발효기간에 따른 품질특성 및 저장성에 관한 연구

김금정 경희대학교 대학원 2019 국내박사

채소류는 일반적으로 즙이 많고 고유한 향미를 지녀서 소비자의 기호를 충족시키고 식욕을 증진 시키지만 수확 후, 저장 중에 지속적인 호흡작용과 미생물의 오염으로 장기저장이 어려워 전통적인 절임법이 개발되었다. 절임식품은 우리나라의 대표적인 전통식품으로 식생활의 중요한 부분을 차지하고 있으나 보존성 측면에서 고농도의 소금으로 염장하므로 다량 섭취 시 건강상의 문제를 야기할 수 있어 대량소비와 발전에 한계를 갖고 있다. 따라서 절임식품이 갖고 있는 문제점들을 해결하여 전통식문화를 발전시키고 대중적인 소비를 유도하기 위하여 현대인들의 기호, 상품성, 건강을 고려한 저염 절임식품의 개발이 품질표준화와 함께 요구되고 있다. 현재에도 시판되고 있는 오이지의 대부분은 연부현상을 억제하기 위한 고염도(5~10% 이상) 용액에서 절여져 짠맛 때문에 우려서 먹어야하는 번거로움과 탈염 시 발효향미성분과 영양성분을 손실하게 되는 것이 문제가 된다. 본 연구에서는 그 문제를 해결하기 위해 저염 오이지의 적정염도로서 1~5%의 소금 첨가량에 따른 오이지의 품질특성을 검토하고자 수분, pH, 산도, 염도, 색도, 경도의 6가지 물리화학적 측정과 관능검사를 실시하였고, 적정 발효기간은 3일부터 7일까지로 하여 오이지의 품질특성을 동일한 방법으로 검토하였다. 또한 함염 식품인 함초와 다시마 분말을 소금 첨가량의 10~40%를 대체, 첨가하여 적정 소금첨가량과 동일한 염도를 나타내는 저나트륨 오이지를 제조하고 품질특성을 측정하였다. 저염, 저나트륨 오이지들의 저장기간을 검토하기 위하여 8주 동안 대조 오이지를 포함한 5 종류의 오이지들을 김치냉장고에 저장하며 저장기간에 따른 이화학적 품질변화를 측정하고 관능적 특성평가를 하여 다음과 같은 결과를 알아내었다. 첫째로, 소금으로만 담근 오이지는 소금 첨가량이 3%인 침지용액에서 담근 오이지가 전체적인 기호도에서 가장 기호도가 높은 결과를 얻었으며 3% 소금 용액에서 담근 오이지는 맛의 기호도에서도 가장 높은 기호도를 보였다. 이와 같은 결과는 3%의 저염으로도 충분히 발효된 맛을 지닌 오이지를 제조할 수 있었고 발효액에서 건져 깨끗한 물로 씻고 저온에서 보관한다면 오래도록 연부현상을 지연시키며 보관이 가능하다는 것을 알 수 있었다. 둘째로, 3%의 침지용액에서 발효시킨 오이지의 발효시간은 5일 발효된 오이지의 전반적인 기호도가 가장 높았으며 맛의 기호도에서도 유의적으로 가장 높았다. 따라서 본 연구에서와 같이 전통적으로 담가먹었던 온도인 27℃에서 오이지를 담글 경우, 5일 정도 발효시키면 충분히 발효되어 기호도가 높은 오이지 제조가 가능하다는 것을 알았다. 셋째로, 소금 농도로는 3% 침지용액에서 기호도가 높은 오이지 제조가 가능하지만 저염식이 요구되는 경우, 더욱 나트륨의 함량을 낮출 수 있는 함염식품으로 소금의 일부를 대체하기위해 함초와 다시마를 선택하여 각각 소금 첨가량의10~40%의 염도를 함초와 다시마로 대체한 오이지를 만들어 품질평가를 한 결과 함초는 독특한 냄새로 인해 10~20%를 대체한 오이지의 기호도가 높았고 다시마는 익숙한 냄새와 다시마의 감미가 더해져 30~40%의 높은 대체량에도 발효맛, 신맛, 경도, 아삭함 등에서 기호도가 높게 나타났다. 또한 높은 기호도로 일상의 섭취가 가능한 함초 10~20% 대체 오이지와 다시마 30~40%의 대체 오이지 및 3% 소금용액에서 발효시킨 대조 오이지의 5가지 샘플에 대한 나트륨 측정을 한 결과, 소금 3% 용액에서 담근 대조 오이지의 나트륨 함량이 가장 높았고, 다시마로 40%를 대체한 오이지는 대조 오이지보다 나트륨 함량이 거의 절반 정도 밖에 되지 않았다. 넷째로, 저염으로 제조한 오이지의 저장가능 기간을 검토하고자 3% 소금 첨가 대조 오이지와 기호도가 높았던 함초 10, 20% 대체 오이지, 다시마 30, 40% 대체 오이지의 5가지 오이지를 김치냉장고(2±1℃)에서 8주 동안 저장하며 오이지의 품질특성을 검토하였고 저장 5주에 관능검사에 의한 품질특성 평가를 하였다. 그 결과 대부분의 오이지는 저장 8주간 동안 수분과 염도의 증가와 감소가 반복되면서 변화하였으나 변화의 시기는 시료에 따라 다르게 나타났다. 이는 오이지를 침지액에서 건져내어 김치냉장고에 보관하였지만 오이지에서 흘러나온 침출액과 오이지 간의 염도 차이로 약간의 삼투압 현상이 작용한 것으로 생각되며 저장 8주째에는 침출된 수분의 양이 많아지고 대부분 염도가 높아졌다. pH와 산도는 대부분의 오이지에서 발효를 중단시켰음에도 불구하고 pH가 낮아지고 산도는 증가하였다. 그 변화의 정도는 시료 간 차이가 있었는데 대조 오이는 pH가 현저하게 떨어지며 산도가 증가한 반면, 함초 첨가 오이지의 경우는 큰 변화가 없었다. 다시마 첨가 오이지의 경우, 40% 첨가된 오이지는 pH 저하와 산도 증가가 현저하였으나 30% 첨가 오이지의 경우 큰 변화는 없었다. 그 이유는 다시마 40% 대체 오이지의 경우 현저하게 낮은 나트륨의 함량에 기인한 것이라고 생각된다. 저장 중 오이지의 색은 대체로 명도는 감소하고 적색도와 황색도는 증가했는데, 함초가 대체된 오이지에서 명도가 가장 크게 감소하였고 적색도도 가장 크게 증가하였다. 경도의 변화는 모든 오이지에서 경도가 감소하다가 증가하는 피크를 이루며 다시 감소하는 현상을 보였다. 경도의 최고 피크는 오이지에 따라 달랐으며 대체로 6주째에 피크를 이루었으나 다시마 40% 대체 오이지는 4주째에 경도가 가장 높았다. 오이지들 사이에 이와 같이 경도의 변화가 다른 양상을 보이는 것은 나트륨 함량의 차이로 인한 삼투압 현상이 다르기 때문이며, 연부현상이 나타나는 시기가 다르기 때문인 것으로 생각된다. 다섯째, 저장 5주째에 실시된 오이지의 관능검사 결과는 소금만으로 담근 대조 오이지가 전반적인 기호도에서 점수가 가장 높았으며, 외관, 냄새, 맛, 텍스처에서도 가장 기호도가 높았다. 발효 초기인 5일간 발효된 오이지의 기호도는 대조 오이지가 함초로 대체된 오이지보다 높았고 다시마가 대체된 오이지보다는 낮았다. 다시마 30, 40% 대체 오이지는 소금만으로 만든 오이지와 소량 대체된 오이지보다 발효맛, 신맛, 경도, 아삭함 등에서 강도가 높게 나타났다. 따라서 저나트륨 오이지를 제조하려고 다시마를 쓸 경우 소량 대체 보다는 30~40%의 고농도로 대체하는 것이 효과적이나 저장 5주 후에는 함초나 다시마가 대체된 오이지보다 소금으로만 담근 대조오이지의 기호도가 자장 높았다. 이러한 결과는 함초와 다시마가 저장 중 군내와 쓴맛을 형성하여 오이지 특유의 상큼한 발효맛을 훼손시켜 기호도가 낮아진 것으로 생각된다. 이상의 결과들로부터 저염 오이지를 제조하고자 할 때, 침지 용액의 소금 농도는 3%가 적정하며, 여름철 상온(27±1℃)에서는 5일간 발효시킴으로써 짜지 않고 맛있는 오이지 제조가 가능함을 알 수 있었고, 저나트륨 오이지 제조 시에는 함초 보다는 다시마 첨가가 더 효과적이나 저나트륨으로 인해 연부현상이 빨리 오므로 저장 기간이 짧은 경우에만 가능하고, 5주 이상 보관할 경우에는 소금으로만 담그는 것이 권장된다. 본 연구는 저염이나 저나트륨 오이지의 새로운 제조 기준과 방법을 제시함에 있어서 식품을 대량 생산하는 제조업체뿐만 아니라 저온시설이 없는 소규모 외식업체에서나 일반 가정에서도 저염, 저나트륨 오이지를 쉽게 제조할 수 있도록 전통적인 발효방법인 상온(27±1℃)에서의 오이지 제조 방법을 제시함으로써 저염 오이지의 신속한 확산을 도모하고자 하며, 그 결과, 시중 어디에서도 저염, 저나트륨 오이지를 쉽게 구매해서 먹을 수 있도록 하여 우리 고유의 전통식품인 오이지에 대한 인식을 새로이 환기시키고 건강한 식생활에 기여하고자 하였다. Vegetables have juicy and unique flavors that meet consumer preferences and satisfy their appetite. However, salting methods have been developed to preserve vegetables for a long time after harvesting because of continuous respiration and microorganism contamination during storage. Salted foods are important components of the human diet and are some of the best-known traditional Korean foods. Nevertheless, there are some limitations on mass-consumption due to preservation with high concentrations of salt, which can cause health problems when consumed in large quantities. Therefore, to develop traditional food culture and encourage public consumption by solving problems associated with salted foods, it is necessary to develop low-salt varieties that consider peoples’ taste preferences, commercial potential, and healthfulness, along with quality standardization. Currently, most commercially available cucumber pickles are salted in high-concentration of salt solutions (5–10% or more) to inhibit softening effects, producing a very salty taste. This method is also problematic because some of the fermented flavor and nutrients may be removed during desalination. To solve these problems, sensory evaluations and six physicochemical measurements of metrics like moisture, pH, salinity, color, and hardness were performed to investigate the quality of pickled cucumbers in terms of salt contents (1–5%) and determine the optimum salinity for low-salinity cucumber pickles. The appropriate fermentation period was chosen to be 3–7 days and identical methods were used for reviewing the quality characteristics of the pickles. Moreover, saltwort (Salicornia herbacea L.) and sea tangle (Laminaria longissima) powder were added to replace 10–40% of the salt content in the low-salinity cucumber pickles to achieved a taste similar to that of regular pickled cucumbers, but with reduced sodium content. The quality characteristics of the low-salinity cucumber pickles were also observed. To investigate the storage periods of low-salinity and low-sodium cucumber pickles, five types of cucumber pickles, including a control batch, were stored in a kimchi refrigerator (designed specifically for storing kimchi) for 8 weeks. Changes in the physicochemical characteristics of the pickled cucumbers were observed as a function of the storage period length and sensory characteristics were evaluated. Of the pickles immersed in solutions containing only salt, the cucumber pickles salted in a 3% salt solution exhibited the best overall properties and the highest taste preference. These results suggested that cucumber pickles with sufficient fermented taste can be produced even with a low-salinity solution of 3% NaCl. Storage with long-term delay of softening is possible if the cucumber pickles are stored at low temperatures after removing from the fermentation broth and washed with clean water. The pickled cucumbers fermented in 3% NaCl solution for 5 days showed the best overall properties and taste preference. Therefore, the fermentation period of 5 days was sufficient to produce well-fermented cucumber pickles with good properties when immersed at the traditional immersion temperature of 27 °C. Ideal cucumber pickles can be produced using an immersion solution containing 3% salt. However, for low-salt diets, glasswort and sea tangle can be used to partially replace salt to lower the overall sodium content. The quality of the cucumber pickles where replaced 10–40% of the salt was replaced with glasswort or sea tangle was evaluated. The cucumber pickles in which 10–20% of the salt was replaced with glasswort showed a high level of preference due to the distinctively characteristic ordor of saltwort. The cucumber pickles where 30–40% of the salt was replaced with sea tangle showed a high level of preference due to its fermented taste, sour taste, hardness, and crispiness due to its familiar aroma and savory taste of the sea tangle. Additionally, sodium contents were measured in the samples (control batch fermented with 3% NaCl solution, cucumber pickles with 10 or 20% of the salt replaced with saltwort, and samples with 30 and 40% of the salt replaced with sea tangle) to determined their suitability for daily intake due to their high preference. The sodium content was the highest in the control batch immersed in the 3% NaCl solution and the sodium content in the cucumber pickles with 40% of the salt replaced with sea tangle was half that of the control. To evaluate the potential storage periods of low-salinity cucumber pickles, 5 types of pickles (control batch with 3% NaCl solution, pickles replacing 10 and 20% of the salt with saltwort and 30 and 40% of the salt with sea tangle) were stored for 8 weeks in a kimchi refrigerator (2±1 °C). After various storage periods, the quality characteristics of the pickles were investigated, and sensory evaluation was performed at the fifth week of storage. As a result, most pickled cucumbers showed a repetitive pattern of the increase and decrease in moisture and salinity level during the 8 weeks of storage, but the time of the change varied depending on the sample’s conditions. This may have resulted from the osmotic pressure arising from the salinity differences between the cucumber pickles and their effluence, even though they were stored in a Kimchi refrigerator after being removed from the immersion solution. After the eighth week of storage, the amounts of discharged moisture and salinity in most batches increased. Even after fermentation stopped, the pH decreased in most batches, but a difference in the degree of change was observed between the samples. The pH of the control batch remarkably decreased. Meanwhile, no significant change in the saltwort-added cucumber pickles was observed. The pickles prepared by replacing 40% of the salt with sea tangle showed a noticeable decrease in pH, whereas those prepared by replacing 30% of the salt showed no significant pH changes. This may have resulted from the significantly lower sodium content in the batches that replaced 40% of the salt with sea tangle. During storage, most pickles exhibited a decrease in lightness and increased redness and yellowness. The pickles fermented in the solution substituted with saltwort showed the greatest decrease in lightness and the greatest increase in redness. The hardness of all pickles decreased initially, then increased to a plateau and subsequently decreased. The highest hardness varied depending on the batch, with most pickles reaching a peak at the sixth week, but those in the solution replacing 40% of the salt with sea tangle showed the highest hardness at the fourth week. The changing patterns of hardness in the batches were due to differences in the osmotic pressure by the varied sodium contents, which resulted in differences between occurrence of the softening effect. Sensory evaluation of the cucumber pickles at the fifth week of storage showed the highest score in terms of overall preference, as well as in appearance, smell, taste, and texture in the control batch immersed in the salt solution. The control pickles fermented for 5 days showed a higher level of preference than those substituted with saltwort and a lower level of preference than those pickled with sea tangle. Cucumber pickles prepared by replacing 30 and 40% of the salt with sea tangle showed higher degrees of fermented taste, sour taste, hardness, and crispiness than those fermented in only salt and with sea tangle replacing some of the salt. Therefore, when sea tangle is used to produce low-sodium cucumber pickles, it is more effective to replace 30–40% of the salt than using lower concentrations. However, after 5 weeks of storage, the preference level of the control batch immersed with only salt was higher than those replacing some of the salt with saltwort or sea tangle. This may have originated from the formation of a stale smell and bitter taste from the saltwort and sea tangle during storage, which masked the unique taste of fermented cucumber pickles and lowered the preference. From the above results, it is clear that the optimum salt concentration of the immersion solution was 3% and 5 days of fermentation at room temperature (27±1 °C) in summer produced delicious low-salinity cucumber pickles. In addition, sea tangle was more effective than saltwort for replacing some of the salt to make low sodium cucumber pickle. However, this beneficial effect only remained for a short period of storage time because low sodium contents resulted in a softening effect. Therefore, immersion in pure salt solution is recommended for storage periods of more than 5 weeks. In this study, novel fermentation standards and methods were developed to easily produce low-salinity and low-sodium cucumber pickles for mass-production food companies and small food service operations and homes without low-temperature facilities. By using conventional fermentation at room temperature (27±1 °C), we aimed to accelerate the wide adoption of low-salinity cucumber fermentation to allow the consumption of low-salinity and low-sodium cucumber pickles in local markets. These methods could give the good change of the perception of traditional Korean food, pickled cucumbers, and contribute to promoting healthy eating habits.

Corynebacterium glutamicum ATCC13032 유래 Flavin-containing Monooxygenase와 변이효소의 정제 및 특성연구

정혜숙 경성대학교 일반대학원 2014 국내석사

A flavin-containing monooxygenase from Corynebacterium glutamicum ATCC13032 (cFMO) was expressed in pMAL-C2X. cFMO was purified as a maltose binding protein(MBP)-fused form by amylose affinity chromatography. The recombinant enzyme showed a temperature optimum at 25℃ and had the highest activity at pH 8.0. According to the absorption spectra of MBP-cFMO in the oxidized and reduced forms, cFMO was classified in a typical flavoprotein and required more than 2 mM of exogenous FAD for maximal enzyme activity. When the effect of several metal ions was determined using trimethylamine as a substrate, 1 mM Cu2+ strongly inhibited FMO activity, and its activity was recoverd by addition of 1 mM EDTA. The enzyme can catalyze the oxidation of trimethylamine, thiourea, and cysteamine, but not glutathione and cysteine. The Km values for trimethylamine, thiourea, and cysteamine are 0.575, 0.38, and 5.95 mM, respectively; Kcat values are 156.1, 40.22 and 110.3 per min, respectively. Inaddition, cFMO had indoxyl-forming activity by oxidation of indole. Escherichia coli expressing cFMO produced 684 mg/l of indigo and 103 mg/l of indirubin in the LB medium containing 2.5 g/l of tryptophan after 36 hr cultivation. In order to increase enzyme activity, 6 types of mutants, A210G, A210S, A210C, S211K, F170Y, and T326S, were constructed based on based on the structure of the FMO protein from Methylophaga aminisulfidivorans and characterized their biochemical characteristics. Of them, T326S mutant showed a great decrease of NADPH oxidation activity (futile activity) in the absence of substrate compared to wild type FMO.

함유황 phytochemical에 의한 benzo[a]pyrene cytotoxicity의 억제

김현정 연세대학교 대학원 2001 국내박사

Allium속 식물의 대표적인 지용성 함유황 phytochemical의 benzo[a]pyrene(B[a]P) 유발 독성에 미치는 영향과 작용 기작을 파악하고자 인간의 대표적인 물질대사 기관인 간 (liver) 유래의 세포 중 HepG2 및 피부세포인 spotaneously immortalized keratinocyte(SIK)에서 B[a]P 유발 독성과 이와 관련된 대사 효소에 대한 영향을 연구하였다. In vitro 배양 조건에서 diallyl sulfide(DAS)와 diallyl disulfide(DADS)는 매우 급격히 휘발하였으며, 휘발성 함유황 phytochemical의 활성 측정을 위하여 포집체로서 α-cyclodextrin, hydroxypropyl-β-cyclodextrin (HP-β-CD) 와 γ-cyclodextrin을 시험한 결과, 모두 allyl sulfides의 B[a]P 독성억제 작용을 증가시켰다. 이 중 HP-β-CD를 함께 처리할 경우 DADS와 diallyl trisulfide(DATS)는 B[a]P에 의해 감소된 세포 생존율을 효과적으로 증가시켰다. B[a]P 유발 독성에 대한 함유황 phytochemical의 보호 기작을 연구하기 위하여 B[a]P의 주된 대사적 활성화 효소인 cytochrome P450 1A subfamily(CYP1As)에 미치는 영향을 조사한 결과 DADS와 DATS는 100 ∼ 1000 μM 농도에서 CYP1As와 cytochrome P450 1B1(CYP1B1)의 지표활성인 7-ethoxyresoru fin-O-deethylase(EROD) 활성을 각각 30∼90% 및 70∼95% 저해하였다. 이들 함유황 phytochemical은 모두 B[a]P을 처리하여 조제한 microsome의 EROD활성에 대해 mixed type inhibitor로 작용하였고 저해정도는 DATS, DADS, DAS순 이었다. 또한 western blotting 결과로부터 B[a]P 처리는 HepG2 cell에서 CYP1B1의 합성을 유도하지 않았으며 DADS와 DATS는 B[a]P처리에 의하여 유도된 CYP1A2 합성을 저해함을 알 수 있었다. 함유황 phytochemical들은 cytosol의 glutathione S-transferase(GST)활성을 유의적으로 증가시키지 않았으며 B[a]P를 처리하여 얻은 cytosol의 GST 활성에도 영향을 주지 않았다. 한편 GST 활성 저해제인 ethacrynic acid와 ketoprofen의 처리는 B[a]P에 의해 유발된 세포 독성을 증가시켰고 GST 활성 증가제인 6-propyl-n-thiou racil은 B[a]P에 의해 유발된 세포 독성을 감소시키는 경향을 나타내었다. 독성 물질의 해독화와 밀접한 관련이 있는 glutathione depletor인 diethylmaleate를 처리하였을 때 B[a]P 유발 독성이 급격히 증가하여 GST와 glutathione은 HepG2 세포의 해독화계에서 중요한 역할을 담당하고 있음을 시사하고 있다. 함유황 phytoch emical의 구조와 B[a]P 유발 독성에 대한 억제 활성과의 관계를 파악하기 위하여 DAS, DADS, DATS등 allyl sulfides 이외에 dipropyl sulfide, dipropyl disulfide, dimethyl sulfide, dimethyl disulfide, allyl methyl sulfide, methyl propyl disulfide 및 S-allyl cysteine을 선정하여 B[a]P에 의해 유발된 세포 독성에 대한 영향을 조사하였다. 그 결과 B[a]P의 세포 독성에 대한 저해 활성에 필수적인 구조는 allyl group이었으며, allyl sulfides중에서는 sulfur 수가 많을수록 B[a]P 유발 독성을 효과적으로 저해하였다. 마늘로부터 지용성 향기성분을 추출하여 제조한 garlic oil의 경우 전체 향기성분 중 allyl sulfides의 함량이 높았으며, B[a]P 유발 세포 독성 및 EROD 활성을 효과적으로 저해하였다. 함유황 phytochemical의 조직 (tissue) 별 작용 특성을 파악하기 위하여 간 이외의 조직 (extrahepatic tissue)으로서 피부세포를 선정하였다. SIK와 human epidermal keratinocyte에서도 DAS와 DADS는 B[a]P의 세포 독성을 감소시켰고 DNA 및 protein과 B[a]P의 adduct 형성을 억제하였다. 이 때의 작용 기작도 주로 EROD활성 감소와 연관된 것으로 생각되고, GST 활성은 유의적으로 증가시키지 않아 간 유래 세포인 HepG2에서의 결과와 같은 양상이었다. The sulfur-containing phytochemicals are typical flavor compounds of Allium vegetables In this thesis, the inhibitory effects of these sulfur-containing phytochemicals on the toxicity induced by benzo[a]pyrene (B[a]P) was investigated in terms of the species-specific metabolism of B[a]P in human hepatic tissue derived cell (HepG2) and extrahepatic tissue derived cell (spontaneously immortalized keratinocyte). The modulatory effects of these phytochemicals on B[a]P metabolizing enzymes was also investigated. In addition, structure-activity relationship of sulfur containing phytochemicals was also studied. It was previously reported that diallyl sulfide (DAS) and diallyl disulfide (DADS) have protective effects on the B[a]P-induced tumorigenesis in animal model. However, it was unable to observe their protective effects in the routine culture condition Sulfur containing phytochemicals such as DAS and DADS are highly volatile compounds. The loss by evaporation during the incubation seemed to be the major reason for the above contradiction between in vitro and animal model study. Cyclodextrins were added to the incubation medium to slow down the evaporation rate by complex formation with the sulfur-containing phytochemicals. As expected, α-cyclodextrin, hydroxypropyl-β-cyclodextrin and λ-cyclodextrin were enhanced the inhibitory effects of sulfur-containing phytochemicals on B[a]P-induced cytotoxicity DADS and diallyl trisulfide (DATS) effectively increased the cell viability in the presence of hydroxypropyl-β-cyclodextrin. The mechanism of the above modulating activity was studied by assaying the cytochrome P450 1A subfamily, which is the primary enzyme responsible for B[a]P activation. The relationship between the inhibition of B[a]P-induced cytotoxicity and ethoxyresorufin-O-deethylase (EROD) activity as a marker enzyme for cytochrome p450 1As and 1B1 was also studied in a human liver-derived cell model. DADS and DATS inhibited the B[a]P-induced EROD activity by 30∼90% and 70∼95% at 100∼1,000 μM concentration, respectively. Sulfur-containing phytochemicals showed the mixed type inhibition pattern on the B[a]P treated microsomal EROD activity Western blotting results indicated that the protein synthesis of cytochrome p450 1A2 was induced by B[a]P in HepG2 cell and inhibited by sulfur containing phytochemicals. However cytochrome p450 1B1 was not induced by B[a]P treatment. Analysis of B[a]P metabolites revealed that the proportion of 7,8-diol formed was reduced in the DADS and DATS treated microsomes relative to the control group. The proportion of 9,10-diol and 4,5-diol formed w as also lowered by the allyl sulfides treatment. Sulfur-containing phytochemicals did not induce or increase the glutathione S-transferase (GST) activity in HepG2 cells. They have no modulatory effects on B[a]P treated cytosolic GST activity Ethacrynic acid and ketoprofen, the inhibitors of GST increased the B[a]P-induced cytotoxicity while 6-propyl-n-thiouracil act as an enhancer for GST activity inhibited the B[a]P-induced cytotoxicity. Diethylmaleate, the glutathione depletor, drastically increased the B[a]P-induced cytotoxicity Several sulfur-containing phytochemicals w ere selected to elucidate the structural features that control the inhibitory potency. The structure variables studied include the number of sulfur atom present, the role of saturation of alkyl substituent and the significance of symmetry. Inhibitory effects of dipropyl sulfide, dipropyl disulfide, dimethyl sulfide, dimethyl disulfide, allyl methyl sulfide, methyl propyl disulfide and S-allyl cysteine suggested that allyl group was essential in inhibitory potency on B[a]P-induced cytotoxicity and the number of sulfur atoms dominate the inhibitory effects of sulfur-containing phytochemicals. Garlic oil was extracted and volatile compositions were analyzed by GC/MS. Diallyl disulfide was the major volatile component of garlic oil but small amount of DAS and DATS were also detected Garlic oil was good inhibitor to the B[a]P-induced cytotoxicity and EROD activity as expected from the allyl sulfides composition. Human epidermal keratinocyte and spontaneously immortalized keratinocyte were selected as model system for human extrahepatic tissue. In these cell models, sulfur-containing phytochemicals such as DAS and DADS inhibited the B(a)P-induced cytotoxicity and adducts formation of B[a]P with protein and DNA. EROD activity was inhibited but GST activity was not increased by sulfur-containing phytochemicals in human keratinocytes. The inhibitory mechanism of sulfur-containing phytochemicals on B[a]P-induced toxicity was related with the inhibition of phase I enzymes and not with the induction of phase II enzymes in hepatic and extrahepatic tissue.

납 함유 입자, 지하철 입자, 표준 광물 입자의 단일 입자 특성 분석

정해진 인하대학교 대학원 2013 국내박사

There are a wide variety of aerosols with different physical and chemical properties in the atmosphere. Being generated from various sources, these aerosols can influence public health and global climate both directly and indirectly. Every year, numerous studies are carried out to assess the chemical compositions of aerosols in various places around the world. Most of those studies rely on bulk analysis procedures which provide only the average compositions of particulate samples. Since atmospheric particles are chemically and morphologically heterogeneous, information concerning the average composition and aerodynamic diameter is not sufficient to describe the population of the particles. Thus, microanalytical methods have proven to be a reliable option for studying atmospheric particles. A quantitative single-particle analytical technique, low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA), has been successfully applied to characterize various types of individual aerosol particles. The low-Z particle EPMA based on SEM/EDX can be used to provide information on morphology and elemental concentrations. Herein, low-Z particle EPMA was applied for the characterization of various airborne particles such as lead-containing, airborne subway, floor dust, and magnetic subway particles. In this dissertation, the first chapter presents the analytical results of ambient sinlgle particles collected near a lead smelter. Aerosol particle samples were collected over a 24-hour period, starting from 8 pm on 31 May 2002, using a high volume TSP sampler. For this near source sample, 73 out of 377 particles (accounting for 19.4%) were identified as lead-containing particles mixed with other species (S, Cl, K, Ca, and/or C), which should have been emitted from a nearby lead smelter. Lead-containing particles of less than 2 µm size in the near source sample accounted for the relative abundances of 42%. SEM-EDX analysis of individual standard particles, such as PbO, PbS, PbSO4, PbCl2, and PbCO3, was also performed to assist in the clear identification of lead-containing aerosol particles. Lead-containing particles were frequently associated with arsenic and zinc, indicating that the smelter had emitted those species during the non-ferrous metallurgical process. The frequently encountered particles following the lead-containing particles were mineral dust particles such as aluminosilicates (denoted as AlSi), SiO2, and CaCO3. Nitrate- and sulfate-containing particles were encountered frequently in 2 – 4 µm size range, mostly in the forms of Ca(NO3, SO4)/C, (Mg, Ca)SO4/C, and AlSi+(NO3, SO4). Particles containing metals (e.g., Fe, Cu, and As) in this near source sample had relative abundances of approximately 10%. Although the airborne particles collected near the lead smelter contained elevated levels of lead, other types of particles, such as CaCO3-containing, carbonaceous, metal-containing, nitrates, sulfates, and fly-ash particles, showed the unique signatures of samples influenced by emissions from the lead smelter. The second chapter presents the analytical results of subway particle samples collected at four underground subway stations in Seoul. To clearly identify indoor sources of subway particles, four sets of samples collected in tunnels, at platforms, near ticket offices, and outdoors were investigated. For the samples collected in tunnels, Fe-containing particles predominated with relative abundance of 75-91% at the four stations. The amounts of Fe-containing particles decreased as the distance of sampling locations from the tunnel increased. In addition, samples were also collected at the platform in subway stations with platform screen doors (PSDs) that limit air-mixing between the platform and the tunnel. The analysis of those samples showed marked decreases in relative abundances of Fe-containing particles, clearly supporting the possibility that Fe-containing subway particles are generated in the tunnel. PM10 mass concentration levels are the highest in the tunnels and decreased systematically with the increasing distance from the tunnel. The extent of the decrease in PM10 in stations with PSDs is also larger than those without PSDs. The results clearly indicate that Fe-containing particles originating from tunnels predominate in the indoor microenvironment of subway stations, resulting in high indoor PM10 levels. As such, PSDs are found to play a significant role in reducing Fe-containing particles at platforms and near ticket offices. In the third chapter, floor dust subway particles were investigated to examine chemical composition of Fe-containing particles in details. Floor dust particles were collected at five sampling locations of an underground subway station, Jegi station, in Seoul, Korea. Size-segregated floor dusts were divided into magnetic and non-magnetic fractions using a permanent magnet. Using X-ray diffraction (XRD) and SEM/EDX, iron metal, which is relatively harmless, was found to be the dominating chemical species in the floor dusts of the < 25 µm size fractions with Mg, Al, Si, Ca, S, and C as minor components. From SEM analysis, the floor dusts of the < 25 µm size fractions collected on railroad ties appeared to be smaller than 10 µm, indicating that their characteristics should be comparable to those of airborne particles in the tunnel and the platform. As most floor dusts are magnetic, PM levels at underground subway stations can be controlled by removing indoor magnetic particles using magnets. In addition, airborne subway particles, most of which were smaller than 10 µm, were collected using permanent magnets at two underground subway stations, Jegi and Yangjae stations in Seoul, Korea. XRD and SEM/EDX analyses showed that most of the magnetic aerosol particles collected at Jegi station was iron metal, whereas those at Yangjae station contained a small amount of Fe mixed with Na, Mg, Al, Si, S, Ca, and C. The difference in composition of the Fe-containing particles between the two subway stations should be attributed to the different ballast tracks used. As the fourth chapter in this dissertation, the speciation of mineral particles was performed on a single particle level for 24 mineral samples, including kaolinite, montmorillonite, vermiculite, talc, quartz, feldspar, calcite, gypsum, and apatite by the combined use of attenuated total reflectane FT-IR (ATR-FT-IR) imaging and low-Z particle EPMA techniques. Although the low-Z particle EPMA is powerful for characterization of individual particles, its limited capability for unambiguous molecular speciation is sometimes disadvantageous. FT-IR is a powerful technique for functional group analysis and molecular speciation of organic and inorgainc chemical compounds. Our previous work (Ryu and Ro, 2009) demonstrated the potential of the combined use of ATR-FT-IR imaging and a quantitative ED-EPMA, low-Z particle EPMA, techniques for the characterization of individual aerosol particles. These two single particle analytical techniques provide complementary information, the ATR-FT-IR imaging on mineral types and low-Z particle EPMA on the morphology and elemental concentrations, on the same individual particles. This work demonstrates that the combined use of the two single-particle analytical techniques can powerfully characterize externally heterogeneous mineral particle samples in detail, while offering great potential for the characterization of airborne mineral dust particles.

Nitrogen-containing carbon support and Palladium-loaded Tungsten carbide catalyst in electrochemical hydrogen oxidation : 전기화학적 수소 산화 반응에서의 질소 작용기를 가진 탄소 지지체와 팔라듐이 담지된 텅스텐 카바이드 촉매에 관한 연구

배강홍 포항공과대학교 일반대학원 2013 국내박사

Platinum metal loaded on carbon has been widely used as a catalyst in proton exchange membrane fuel cell. However, durability and cost problems delay the commercialization of this system. To solve these problems, my researches have been focused on the catalyst and support materials. Nitrogen-containing carbon materials were prepared by acetonitrile pyrolysis on carbon black and used as a support for a Pt catalyst. The Pt particles on N-containing carbon exhibited increased activity and stability in electrochemical hydrogen oxidation relative to Pt on pristine carbon black. The N-doped carbon had a graphitic structure and contained pyridinic and quaternary nitrogen species. The Pt nanoparticles were better-dispersed because of increased hydrophilicity induced by the nitrogen species. And the Pt/N-containing carbon showed higher stability in a potential cycling test than Pt/C, because of an increased metal-support interaction. Using XPS and EELS mapping, I demonstrated that the metal-support interaction became stronger and more specific by adding nitrogen into carbon. Although the carbon oxidation problem could be somewhat relieved by N-doping, carbon black has micropores mostly. Thus it is not adequate for a reaction, because the existence of mesopores is important to make triple-phase boundary for fuel cell reaction. Thus I synthesized mesoporous carbon and N-containing mesoporous carbon using resorcinol, formaldehyde, cetyltrimethylammonium bromide, Ludox and urea. And then loaded 20 wt % Pt on them by polyol method using ethylene glycol. TEM images show that Pt particles loaded on N-containg mesoporous carbon are more dispersed than mesoporous carbon like N-containing carbon black. Although they showed a little higher hydrogen oxidation activity to the commercial Pt/C, both of them were inadequate to replace the commercial Pt/C. Therefore, I tried to find another catalysts. Tungsten carbide/mesoporous carbon composite material was synthesized by using resorcinol, formaldehyde, cetyltrimethylammonium bromide and Ludox HS-40 and used as a support for Pd catalyst. Non-modified Pd (Pd) particles were loaded on the carbon black, mesoporous carbon and tungsten carbide/mesoporous carbon composite by using NH3-mediated polyol reduction method and phosphorus-modified Pd (Pd(P)) particles were also loaded on the supports by the same reduction method with the aid of sodium hypophosphite. The sizes of Pd and Pd(P) particles loaded on the mesoporous carbon were smaller than those of Pd and Pd(P) particles loaded on the carbon black because of the high surface area of the mesoporous carbon and thus showed larger hydrogen oxidation activity. In the case of tungsten carbide, the sizes of Pd and Pd(P) particles loaded on the tungsten carbide/mesoporous carbon composite were similar and a little smaller than those of Pd and Pd(P) loaded on the mesoporous carbon but the hydrogen oxidation activity was largely increased by the strong metal - support interaction between the Pd and the WC. Especially, Pd(P) loaded on the tungsten carbide/mesoporous carbon composite showed larger hydrogen oxidation activity than the commercial Pt/C catalyst. Through XRD, TEM-EDX and XPS, I demonstrated that the phosphorus existed mostly as a phosphate group on the supports. Thus the attractive interaction between the Pd precursor, [Pd(NH3)4]2+ and the phosphate group, PO43- makes small Pd(P) nanoparticles and thus maximizes the Pd(P) particles dispersion on the supports compared to the Pd particles. Through the strong metal - support interaction and the phosphorus modification, Pd(P) loaded on the tungsten carbode/mesoporous carbon composite showed a possibility for replacing commercial Pt/C catalyst in the anode of proton exchange membrane fuel cells.

Effects of Sex and Feeding Diets Containing Alfalfa, Laver of Pine-needle meal on the Plasma Cholesterol Level and Cecal Urease Activity in Rats : 알파파, 김 또는 솔잎 粉末을 含有한 飼料의 給與가 쥐의 性別 血中 Cholesterol 含量 및 腸內 Urease Activity에 미치는 影

이종언 濟州大學校 大學院 1996 국내박사

이 硏究는 알팔파, 김 또는 솔잎 粉末을 含有한 飼料의 給與가 쥐의 性別 Plasma Cholesterol 含量 및 Cecal Urease Activity 에 미치는 影響을 究明하기 위하여 實施되었다. 24마리의 암쥐와 24마리의 숫쥐(平均體重 92g)를 2×4 要因實驗으로 配置하고 對照區 또는 實驗飼料를 4주동안 給與하였고 모든 實驗飼料에는 0.5% Cholesterol 를 添加하였으며 알팔파, 김 또는 솔잎분말을 Corn Starch에 代置하여 각각 10% 씩 添加하였다. 4주의 飼養實驗이 끝난후 쥐들을 屠殺하여 血液과 腸 內容物을 採取하여 分析하였다. ADFI 와 ADG 는 김을 급여한 쥐가 알팔파나 솔잎을 급여한 쥐에서보다 높았으며(P<.05) 또한 숫쥐가 암쥐에 비해 현저히 增加하였고(P<.001) F/G는 낮았다(P<.01). 總 盲腸의 무게 및 盲腸 內容物의 무게는 김이나 솔잎을 給與한 쥐가 對照區나 알팔파를 給與한 쥐보다 增加하였다(P<.001). 김을 給與한 쥐가 對照區에 비해 血中 總 Cholesterol 含量이 떨어졌으며(P<.01) 솔잎을 給與한 쥐는 다른 처리구에 비해 血中 總 Cholesterol 含量을 2배 이상 增加시켰다(P<.001). 또한 암쥐가 숫쥐에 비해 2 ∼ 3배 정도 總 Cholesterol 含量을 높였다(P<.001). 알팔파를 給與한 쥐가 김이나 솔잎을 給與한 쥐보다 血中 HDL Cholesterol 含量을 增加시켰으며 (P<.05) 숫쥐가 암쥐보다 HDL Cholesterol 含量이 높았다(P<.001). 血中 Triacylglycerol 含量은 處理나 性間에 큰 차이가 없었으나 솔잎을 給與한 암쥐에서 현저히 增加하였다(P<.001). 盲腸 內容物中의 그램 당 Urease Activity 는 김이나 솔잎을 給與한 쥐에서 현저히 떨어졌으나(P<.001) 總 盲腸內容物 中의 Urease Activity 는 處理間에 有意的인 차이를 보이지 않았다. 그러나 숫쥐가 암쥐에 비해 總 盲腸內容物 중의 Urease Activity 가 높았다(P<.01). 血中 Urea 濃度는 암쥐가 숫쥐에 비해 현저히 增加하였다(P<.001). 本 實驗의 結果를 綜合해보면 김이나 솔잎은 가용성 섬유소가 많이 含有되어 발효과정에서 盲腸의 크기를 增加시킴을 알 수 있고 김은 혈중 Cholesterol 함량을 떨어뜨리나 솔잎은 장내에서 Cholesterol 吸收를 촉진시키거나 體內 Cholesterol 代謝에 큰 影響을 미친다는 것을 알 수 있다. 암쥐가 숫쥐보다 血中 Cholesterol 含量이 높은 것은 암쥐가 숫쥐보다 體重 增體當 Cholesterol를 많이 攝取했고 또한 飼料中 다량의 Cholesterol 을 添加할 때 암쥐가 민감하게 反應함을 보여준다. 따라서 飼料中 特性이 다른 纖維素들이 Cholesterol 이나 Urease Activity에 미치는 影響은 복잡하며 보다 精密하고 다양한 硏究가 必要하다고 思料된다. This study was conducted to investigate the effect of sex and feeding diet containing alfalfa, laver or pine-needle meal on the plasma cholesterol level and cecal urease activity in rats. Four groups of Sprague Dawley rats (initial mean weight, 92 g), each group consisting of six male and 6 females rats, were fed a control or experimental diets, respectively. All the diets contained 0.5% added cholesterol, 5% corn oil and 5% lard. After a 4-week feeding period, rats were killed and cecal contents and plasma samples were collected. Rats fed the control or diets containing laver meal had higher (P<.Ol ) average daily feed intake (AFDC) and average daily gain (ADD) and lower feed/gain ratio (I/G) than rats fed diets containing alfalfa and pine-needle meal. Plasma total cholesterol level in rats fed diet containing pine-needle meal was twice (P<.O1) that in rats fed the other diets. Diet containing laver meal decreased (P<.O1) the plasma cholesterol level, as compared to the control. A significant difference (P<.001) in plasma cholesterol was found between male and female rats. Female rats showed two to three-fold higher plasma cholesterol levels than male rats, regardless of diet. Diet containing alfalfa meal increased (P<.O1) the serum HL cholesterol compared to diets containing laver and pine-needle meal. Interestingly, HDL cholesterol was significantly (P<.O1) higher (2.5 to 3.5-fold) in male thin in female rats. Female rats fed diet containing pine-needle meal had higher (P<.O1) serum triacylglycerol than their male counter pints and rats (male+female) fed the other diets. Ammonia concentration (um ammonia pen g collected contents) in the contents (blink) was higher (P<.05) in the control thin in the other groups. Unease activity (um ammonia produced from unea/30 min pen g contents) in rats fed diets containing liven and pine-needle meal was much lower (P<.Ol) thin that in rats fed the control on alfalfa meal diet, but was not different between sexes. However, total unease activity in the contents was not significantly different between the dietary treatments on sexes. The present studies suggest that dietary soluble fibers such is that in liven decreases plasma cholesterol and cecil unease activity. Feeding a diet containing pine-needle meal increases plasma cholesterol level for-unknown reasons. Female rats respond to dietary cholesterol much greatly, compared to male rats.

Selective translational regulation of premature termination codon containing mutant mRNAs

김원규 Graduate School, Yonsei University 2015 국내박사

Abnormal mRNAs containing premature termination codons (PTCs) are normally degraded through nonsense-mediated mRNA decay (NMD) at the posttranscriptional level, thus preventing the production of potentially harmful truncated mutant proteins. However, NMD is known to be imperfect. The mRNAs containing PTCs in the last exon (NMD-irrelevant) are not recognized by NMD, so they are not degraded. About 10%-30% of NMD-competent PTC-containing mRNAs are resistant to NMD (NMD-resistant) and exist as stably as their PTC-free counterparts. Moreover, if NMD is inhibited by endogenous or exogenous ways, PTC-containing mRNAs to be degraded are expected to be rescued from NMD (rescued PTC-containing mRNAs). These NMD-irrelevant PTC-containing mRNAs, NMD-resistant PTC-containing mRNAs and rescued PTC-containing mRNAs from NMD are the potential sources for the generation of mutant proteins. Therefore, it has been urged to clarify whether mutant proteins are generated from the PTC-containing mRNAs, but detailed molecular mechanisms have been poorly understood. In this study, to clarify whether mutant proteins from the NMD-irrelevant PTC-containing mRNAs are produced, I identified 29 genes with frequent frameshift mutations in the last exon in colon cancers with high microsatellite instability (MSI-H) and selected three genes (TTK, TCF7L2, and MARCKS) for NMD-irrelevant PTC-containing mRNAs and protein expression analysis. The NMD-irrelevant PTC-containing mRNAs from these mutated genes were not degraded by NMD. However, only faint amounts of endogenous mutant TTK and TCF7L2 were detected, and I failed to detect endogenous mutant MARCKS. By polysome analysis, I demonstrated that NMD-irrelevant PTC-containing mRNAs are actively translated and inhibition of the proteasomal degradation facilitated the rescue of endogenous mutant TTK, TCF7L2, and MARCKS. By comparing the expression of neopeptide-containing or neopeptide-lacking truncated mutant proteins derived from genomic MARCKS constructs containing nonsense or frameshift mutations, I demonstrated that the enhanced degradation of these mutant proteins was driven by neopeptides. To demonstrate the generation of mutant proteins from NMD-resistant PTC-containing mRNAs and rescued PTC-containing mRNAs from NMD, human genomic β-globin expression constructs with nonsense mutations were used in order to avoid enhanced degradation of neopeptide-containing mutant proteins derived from frameshift mutations and I found that about 30 % of PTC-containing mRNAs are resistant to NMD in steady-state and these NMD-resistant PTC-containing mRNAs showed similar stability with their PTC-free counterparts. I demonstrated that the NMD-resistant PTC-containing mRNAs were translationally repressed and therefore, only trace amount of detected mutant proteins was generated from the pioneer round of translation step. Moreover, I found that PTC-containing mRNAs were significantly rescued when NMD was inhibited by down-regulating hUPF1, a key NMD factor and a large amount of mutant proteins from the rescued PTC-containing mRNAs was generated from the bulky translation step. I further demonstrated that down-regulation of UPF1 plays key roles to relieve the translational repression of PTC-containing mRNAs. In conclusion, I found 1) NMD-irrelevant mutant mRNAs containing PTC in the last exon are not degraded by NMD in cells and translated efficiently. 2) Truncated proteins containing neopeptides are rarely detected because of extensively degradation by the ubiquitin?proteasome system which is caused by neopeptides. 3) About 30% of PTC-containing mRNAs from NMD-competent β-globin expression constructs are resistant to NMD and exist as stably as their PTC free counterparts. 4) NMD-resistant PTC-containing mRNAs are translationally repressed and trace amount of mutant proteins from them is mainly generated from the pioneer round of translation step. 5) Mutant proteins from the rescued PTC-containing mRNAs from NMD by UPF1 down-regulation are mostly generated from bulky translation. 6) UPF1 plays key roles in the selective translational regulation of PTC-containing mRNAs depending on NMD status. These findings suggest that PTC-containing mRNAs are the pool of the sources for the mutant protein generation and are subject to differential translational and posttranslational regulations depending on NMD status. 일반적으로 조기종결코돈을 포함하는 돌연변이 mRNA는 nonsense-mediated mRNA decay (NMD) 라는 기전에 의해 전사 후 조절되어 잠재적으로 위험한 돌연변이 단백질의 생성을 차단한다. 그러나 NMD는 불완전한 기전으로 알려져 있다. 마지막 exon에 조기종결코돈을 포함하는 돌연변이 mRNA는 NMD에 의해 인식되지 않아 이것들로부터 돌연변이 단백질 생성을 예측할 수 있다. 또한 약 10%~30% 정도의 NMD에 의해 인식되는 조기종결코돈을 포함하는 돌연변이 mRNA는 밝혀지지 않은 기전에 의해 NMD에 저항성을 보이며 정상형 mRNA와 유사한 안정성을 보인다. 특히 NMD는 생리적인 또는 외부의 여러 환경에 의해 저해되는 경우가 많아, 이러한 경우 NMD에 의해 분해되고 있던 조기종결코돈을 포함하는 돌연변이 mRNA가 살아남을 수 있고, 이렇게 세포 내 NMD 저항성 mRNA나 NMD로부터 살아남은 mRNA들은 모두 돌연변이 단백질을 만들 수 있는 잠재적 근거가 될 수 있다. 본 연구에서는 조기종결코돈을 포함하는 돌연변이 mRNA를 돌연변이 단백질 생성 가능성과 연관하여 NMD 무관 조기종결코돈 포함 mRNA, NMD 저항성 조기종결코돈 포함 mRNA, NMD로부터 살아남은 조기종결코돈 포함 mRNA로 분류하고 각각의 경우 돌연변이 단백질의 생성에 대해 규명하였다. NMD 무관 조기종결코돈 포함 mRNA로부터 돌연변이 단백질 생성에 대한 경우, 빈번한 돌연변이를 보이는 현미부수체불안정형 대장암에서 frameshift 돌연변이에 의해 마지막 exon에 조기종결코돈을 갖는 29개의 유전자를 발굴하고 이들 중 3개의 유전자 TTK, TCF7L2, MARCKS를 선정하여 각각 돌연변이 mRNA와 단백질의 발현을 분석하였다. 돌연변이를 TTK, TCF7L2, MARCKS 유전자로부터 발현되는 NMD 무관 조기종결코돈 포함 mRNA는 모두 NMD에 의해 분해되지 않고 안정적으로 존재하였으나, 돌연변이 단백질은 거의 확인되지 않았다. Genomic MARCKS 발현 벡터를 이용한 Polysome 분석을 통해 NMD 무관 조기종결코돈 포함 mRNA가 정상적으로 번역되고 있으며, 이러한 돌연변이 단백질은 생성 후 proteasome 시스템에 의해 빠르게 분해되고 있다는 사실을 규명하였다. 또한 이러한 돌연변이 단백질의 분해 촉진은 c-terminal 부위에 존재하는 비정상형 neopeptide 때문이라는 사실을 확인하였다. 한편, NMD 저항 조기종결코돈 포함 mRNA와 NMD로부터 살아남은 조기종결코돈 포함 mRNA로부터의 돌연변이 단백질 생성을 규명하기 위해 조기종결코돈을 포함하는 사람 β-globin 유전자 발현 벡터를 이용하여 mRNA와 단백질의 발현을 분석하였다. 그 결과, 약 30% 정도의 NMD 저항 조기종결코돈을 포함하는 mRNA가 NMD에 저항성을 보이며 정상형 mRNA만큼 안정적으로 존재하는 것을 확인하였다. 그러나 이렇게 안정한 NMD 저항 mRNA로부터는 오직 극미량의 돌연변이 단백질만을 확인할 수 있었고, 이는 NMD 저항 mRNA의 번역이 억제되어 있으며, 극미량의 돌연변이 단백질은 pioneer round of translation 중 scan 과정에서 생성 되었다는 사실을 규명하였다. 또한 NMD의 주요 구성 요소인 UPF1을 저해하여 NMD를 억제하였을 때, 조기종결코돈을 포함하는 mRNA가 살아남는 것을 확인하였고, bulky translation 과정으로 들어가 많은 양의 돌연변이 단백질을 생성한다는 사실을 규명하였다. 또한 이러한 조기종결코돈을 포함하는 돌연변이 mRNA의 번역을 억제하는 전반에는 UPF1이 핵심적인 역할을 한다는 사실을 확인하였다. 이러한 결과들은 조기종결코돈을 포함하는 mRNA들이 NMD에 관련 또는 무관하게 돌연변이 단백질을 만들어낼 수 있는 잠재적 물질이라는 사실을 보여준다.

경기 일부 지역 고등학생의 카페인 함유 식품 섭취 연구

어유미 수원대학교 2022 국내석사

Caffeine is an ingredient that is widely contained in modern people's favorite foods. According to the 2019 Youth Health Behavior Survey, the intake of high-caffeinated beverages more than three times a week among adolescents was 3.3 percent in 2015, 8 percent in 2017, and 12.2 percent in 2019. Currently, the labeling regulation for high caffeine is applied only to liquid foods manufactured and processed using caffeine-containing raw materials, and there is no regulation on the labeling of caffeine content, making it difficult to maintain and secure the health of teenagers due to excessive caffeine. Therefore, this study tried to use caffeine-containing foods as basic data for future nutrition education so that teenagers can purchase and consume caffeine-containing foods at a safe level by examining the relationship between high school students' caffeine-containing foods. This study was approved by the IRB to explain the purpose of the study to the survey subjects and record it directly with consent, and a survey through a non-face-to-face channel was used to prevent the spread of infectious diseases (COVID-19). General (5 questions), awareness and intake of caffeine-containing foods (9 questions), confirmation of food labeling (3 questions), and nutrition education related to caffeine (6 questions) were investigated, and data processing and statistics were analyzed using IBM SPSS Statistics. The study found that the average daily caffeine intake for caffeine-containing foods was 50.11mg, higher than the average daily caffeine intake of teenagers aged 13-18 (under 13-18) calculated by the Ministry of Food and Drug Safety. In addition, to reduce caffeine intake, decaffeinated foods are consumed, but they are consumed without knowing the exact meaning of decaffeinated. In addition, even if the "food mark" or "caffeine content per serving" and "caution phrase" were not checked or confirmed when purchasing food, it did not affect the purchase and intake of caffeine-containing foods. So far, the results of caffeine-related nutrition education have been high, and the percentage of respondents who answered, "The necessity of caffeine-related nutrition education in the future" and "nutritional education will help choose caffeine-containing foods." Since teenagers purchase and consume caffeine-containing foods outside of school, it is considered more important to develop and educate caffeine-related food labels to help them choose, purchase, and consume caffeine-containing foods so that teenagers can recognize themselves as caffeine-containing foods. Therefore, it is necessary to apply caffeine-related labeling standards to caffeine-containing foods such as ice cream, bread, and snacks, and to provide information on all foods containing caffeine by stipulating the labeling criteria. The limitations of this study are as follows. First, it is difficult to standardize the questionnaire of this study as it was prepared by the researcher by modifying it according to this study by referring to related previous papers. Second, this study is difficult to generalize to all high school students across the country because male and female high school students were randomly selected and studied at high schools in some regions of Gyeonggi-do. Third, since this study investigated only some items of caffeine-containing food, it is difficult to represent the total caffeine-containing food intake of high school students. Therefore, in the follow-up study, the scope of the survey subjects was expanded to a standardized questionnaire, and a study was conducted to understand the correlation between factors on caffeine intake and caffeine intake in various ways through a survey through subdivided caffeine-containing food items.

Evaluation of the thermally induced volatile profiles of fatty acid and amino acid mixtures

Choi, Hyungseok Sungkyunkwan University 2023 국내박사

지질은 마이야르 반응에 참여함으로써 전체적인 휘발성 성분의 조성에 영향을 미치고 다양한 새로운 휘발성 성분을 생성한다. 그러나 조리시에 생성되는 휘발성분에 대한 특정 아미노산 또는 지방산의 기여는 아직 잘 알려져 있지 않다. 본 연구에서는 올레산과 리놀레산이 20개의 아미노산과 반응하여 생성된 휘발성 성분과 전반적인 조성변화를 GC/MS와 전자코를 활용하여 확인하였다. ASP, GLU, TYR을 제외한 모든 검체는 지방산 종류에 관계없이 대조군에 비해 알데히드 함량이 유의적으로 감소하였다. 반면 PRO와 CYS에서는 모든 종류의 알데하이드가 전혀 검출되지 않았다. 알데하이드의 감소는 알데하이드가 아미노산과의 반응을 위한 기질로 참여했음을 의미한다. 아미노산의 종류에 따라 알데하이드와의 반응성이 크게 달랐고 반응에서 생성되는 생성물의 결과도 다양했다. 아미노산과 지방산 반응의 결과물로써 nitrigen-containing comopounds (NCCs), sulfur-containing comopounds (SCCs), 스트레커 알데하이드, 메틸케톤 등이 검출되었다. 스트레커 알데하이드의 형성은 지방산이 산화되어 생성된 디카보닐 성분이 아미노산과 반응함을 의미한다. 스트레커 알데하이드는 올레산과 리놀레산 시스템 모두 4가지의 샘플 (LEU, ISO, PHE과 VAL)에서 높은 비율로 형성되었다. 피리딘과 피롤은 지방산과 아미노산 모델에서 확인된 주요 NCC였고, 샘플마다 다른 종류의 NCC들이 확인되었다. 2-펜틸 피리딘은 리놀레산 모델에서만 검출되었으며 PRO를 제외한 모든 검체에서 발견되었다. 반면에 피롤의 형성은 아미노산의 종류에 영향을 받았다. 특정 아미노산 샘플은 지방산의 종류에 관계없이 동일한 피롤 화합물을 생성했다. 각 시료에서 생성된 대표적인 피롤 성분은 GLY(1-메틸 피롤), ALA(1-에틸-피롤), ISO(1-프로필-2-피롤), VAL(2-메틸 피롤), PRO(1-메틸 피롤, 1-부틸-피롤, 3-메틸-2-피롤, 1-펜틸-피롤, 1-피롤)이다. 메틸 케톤은 특색이 있는 향 성분이며, 이는 전체적인 향에 영향을 미친다. 리놀레산보다 올레산에서 더 많은 종류의 케톤이 검출되었으며, 아미노산 종류에 따라 다양한 경향성의 결과를 보여주었다. 알데하이드와의 반응성이 높은 PRO, LYS 과 ARG에서 특히 높은 함량의 메틸케톤이 검출되었다. 황을 포함하는 아미노산인 CYS와 MET 샘플에서는 다량의 NCC, SCC, 메틸케톤이 검출되었다. CYS에서는 총 11종의 SCC가 관찰되었고, MET에서는 4종의 SCC가 검출되었으며, MET에서는 메테인티올, 디메틸설파이드, 3-(메틸티오)-프로파날 등의 단순한 SCC가 생성되는 반면, CYS에서는 티아졸 류의 질소를 함유하는 SCC이 함께 생성되었다. 올레산과 리놀레산을 혼합한 실험의 결과를 통해 실제 식품처럼 다양한 지방산과 복잡한 성분을 혼합한 경우에도 아미노산 종류에 따른 휘발성분 결과가 적용될 수 있는 가능성을 확인했다. 이 연구는 최초로 특정 아미노산과 지방산으로부터 생기는 향성분인 NCC, SCC, 메틸 케톤 및 기타 휘발성 물질에 대해서 체계적인 분석을 진행하였으며, 이 결과를 통해 실제식품에서의 휘발성분 형성을 보다 과학적으로 설명할 수 있게 되었다. Lipid affects the overall composition of volatile components by participating in the Maillard reaction and produces a variety of new volatile components. However, the contribution of specific amino acid or fatty acid on the volatiles were not well understood yet. In this study, the overall results of the volatile components produced by the reaction of oleic acid and linoleic acid with 20 amino acids were analyzed by solid phase microextraction-GC/MS and electronic nose. Pyridines and pyrroles were the major nitrogen-containing compounds (NCCs) identified from the reaction of fatty acid and amino acid. Total nitrogen-containing compounds were high in glycine, alanine, isoleucine, valine, proline, and cysteine samples. 2-Pentyl pyridine was only detected in linoleic acid models and detected in all samples except proline. On the other hand, the formation of pyrrole compounds was affected by the type of amino acid regardless of the type of fatty acid. Out of amino acid samples, proline sample produced the most diverse NCCs including pyrrole compounds. Significant decrease in aldehydes and increases in methyl ketone were observed after reaction in most samples except aspartic acid, glutamic acid, and tyrosine (p<0.05). Especially in proline and cysteine samples, any aldehydes were not detected, which means all the aldehydes reacted to form new volatile compounds. Methyl ketone is a distinctive aromatic component, which affects the overall aroma. More types of methyl ketones were detected in oleic acid model than in linoleic acid model, and the results were varied depending on the type of amino acid sample. Proline, arginine, and lysine samples showed high contents of methyl ketones in both linoleic acid and oleic acid models. Cysteine and methionine samples produced a large amount of sulfur-containing compounds (SCCs) after reacted with fatty acids. The content of total SCCs showed higher results in methionine sample, whereas more diverse SCCs containing nitrogen molecule such as thiazoles were detected in cysteine sample only. The volatiles of oleic acid and linoleic acid mixture model showed coherent results with that of oleic acid or linoleic acid, suggesting that the results of this study can be applied to real foods composed of various fatty acids and amino acids. With the results of this study, the formation of odor active NCCs and other volatiles in foods can be explained more scientifically. The volatile production of NCCs, SCCs, and methyl ketones can be explained successfully by using the thermal reaction of specific fatty acids and amino acids, which is a unique and novel approach for the understanding the odor active volatiles in real food containing lipids and amino acids.

Fundamentals of crystallization characteristics during the solidification of cr-containing slags

김기범 Graduate School, Yonsei University 2022 국내박사

크롬 함유 슬래그는 잠재적으로 토목, 건설 재료, 철강 공정 내 재활용 등의 방법으로 활용될 수 있는 재료인 반면 환경에 직접적으로 배출될 경우 크롬 산화물의 침출 특성으로 인해 6가 크롬이 생성될 수 있기 때문에 환경과 생태계 오염을 고려한 슬래그 처리 방법이 매우 중요하다. 또한 최근 철강산업에서 지속적으로 증가하는 고성능 스테인리스 강에 대한 수요와 전세계적으로 지속 가능한 친환경 공정을 위한 규제 강화, 자원 재활용에 대한 관심 증대로 인해 크롬 함유 슬래그의 활용과 처리 방법에 대한 연구가 더욱 필요한 실정이다. 용융 슬래그의 결정화 거동은 슬래그의 고온 물리화학적 특성을 결정하는 중요한 요소로써, 결정화 특성의 제어를 통하여 슬래그 내 크롬 안정화와 회수를 위한 기술의 한계를 극복할 수 있을 것으로 판단된다. 이를 위해 크롬 함유 슬래그의 결정화 특성에 대한 기초적인 연구와 더불어 실제 산업 슬래그를 이용한 재활용 가능성을 제시하고 침출 실험, 열역학적 평가를 통한 검토를 실시하였다. 본 연구에서는 슬래그의 선택적 결정화 현상을 통한 고온 용융 슬래그의 응고 거동에서 나타나는 결정화 특성을 분석하였다. 고온 공초점 현미경과 시차 주사 열량계를 활용하여 크롬 산화물과 철 산화물 조성 변화와 다양한 냉각 조건에 따른 결정화 거동을 관찰하였으며 결정 형상에 대한 규명과 핵 생성 및 결정 성장에 대하여 속도론적 분석을 실시하였다. 또한 X선 광전자 분광법과 라만 분광법을 활용하여 결정화 특성의 변화가 비정질 슬래그의 구조 변화에도 기인함을 확인하였다. 산업 스테인리스 강 슬래그와 분진을 활용하여 용융 상태의 슬래그, 분진 혼합물로부터 생성되는 스피넬 초정상 내에 철, 크롬, 망간 등의 유가 금속이 선택적으로 집중되어 결정화 되는 현상을 규명하였으며, 이를 대용량 실험을 통해서도 분석하여 산업 스테인리스 강과 분진에 대한 재활용 가능성도 확인하였다. 또한 슬래그 조성에 의존하여 생성되는 스피넬 결정상의 분율에 따라 스피넬 결정상 내 크롬이 안정화 되어 산 용액 내에 크롬 침출이 억제되는 것을 규명하였으며 이를 열역학적인 계산을 통한 각 결정상의 안정성 도표를 도출하여 검토하였다. Cr2O3-containing slags have the potential to be utilized as an additive for internal reuse of slags, building materials, civil construction, which are directly discharged to the environment, leading to a waste of potential Cr resources. The existence of Cr2O3 and its leaching characteristics limit their broad use due to their environmental effects. With the increasing demand for high-performance stainless steels and a growing importance on environmental friendly processes and sustainability, the treatment of Cr-containing slags and the development of economical and effective methods to improve the efficiency of Cr recovery from slags have been widely studied, including selective crystallization and hydrometallurgical leaching. However, these developments require a fundamental understanding of the thermophysical properties of slag melts. The comprehensive change in the slag composition has a dramatic impact on the thermochemical and thermophysical properties of the slags, including refining ability, heat capacity, density, viscosity, and crystallization behavior. Understanding and controlling these properties is essential to determining the efficiency of slag recycling and cost-effectiveness of the overall process. Particularly, in the manufacturing and refining of Cr-containing metals such as stainless steels or alloyed steels, the crystallization of Cr-containing slag is the most important thermophysical property governing the fluidity and recovery of Cr and has a significant effect on slag tapping, fluidity and mineralogical phase stability. For a sustainable and environmentally friendly process, high chromium recovery through selective crystallization would be beneficial in saving raw materials and energy as well as in reducing eventual chromium pollution from Cr-containing slags and wastes. In this work, the crystallization behavior of Cr-containing slags in the CaO-SiO2-MgO-Al2O3-FetO system was investigated using the CLSM (confocal laser scanning microscope) and DSC (differential scanning calorimetry). Comparison of the shifting trends in the CCT curves with the melt structure that is indirectly assessed through the as-quenched amorphous structure measured using Raman spectroscopy and XPS (X-ray photoelectron spectroscopy). Observation of the morphology of the crystalline phase at high temperatures and the study of the crystallization kinetics was carried out and the precipitated phase was identified using SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy) and XRD (X-ray diffraction) analyses. Also, the selective elemental concentration of valuable metal cations such as Cr, Fe, Mn, Ni in FetO-Cr2O3-NiO-MnO-containing industrial stainless steel slags and dust mixture has been studied. The hazardous metal cations Fe, Cr, Ni and Mn could be locally concentrated during the solidification of a molten stainless steel slag and dust mixture from high temperatures by controlling the primary crystalline spinel phase. The mixture of stainless steel slag and dust samples were quenched at various cooling temperatures and with varying amounts of dust to identify and optimize the crystalline phases using SEM-EDS and XRD analyses. And thermodynamic calculations were carried out to construct the phase stability diagram as a function of pH value to evaluate the potential leaching behavior of Cr-containing slags. And the leaching experiments were performed using hydrochloric acid and Cr-containing slags samples. The amount of Cr-related ions in the leachate was analyzed by ICP-MS (inductive coupled plasma mass spectrometer). The concentration of leached Cr, Fe was compared according to the Cr-enriched spinel phase fraction.