Synthesis of Poly(glycerol-succinic acid)-dithiocarbamate and Poly(glycerol-succinic acid)-1,3,4-thiadiazole Dendrimers and Their Use as Anti-Wear Oil Additives

Kim, Yeong-Joon,Hoang, Quoc-Viet,Kim, Sung-Ki,Cho, Chang-Yong,Kim, Jeongkwon,Chung, Keun-Woo,Kim, Young-Wun Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.7

A series of poly(glycerol-succinic acid) dithiocarbamate and 1,3,4-thiadiazole dendrimers, which have potential as anti-wear oil additives, were synthesized. Their anti-wear properties in three different oils (100N, DB-51, and soybean) were evaluated using a four-ball wear tester. The results indicated that thiocarbamate dendrimers have moderate anti-wear properties in DB-51 oil, and 1,3,4-thiadiazole dendrimers exhibited good anti-wear properties in 100N and DB-51 oils. However, dithiocarbamate and 1,3,4-thiadiazole dendrimers were not effective anti-wear additives in soybean oil.

Effect of centrifugation on tryptic protein digestion

Kim, Soohwan,Kim, Yeoseon,Lee, Dabin,Kim, Inyoung,Paek, Jihyun,Shin, Dongwon,Kim, Jeongkwon The Korean Society of Analytical Science 2017 분석과학 Vol.30 No.2

This study investigated the effect of centrifugation on tryptic digestion. This was done by applying different centrifugation speeds (6,000, 8,000, 10,000, 20,000, and $30,000{\times}g$) over various durations (0, 10, 20, 30, 40, 50, and 60 min) to digest two model proteins - cytochrome c and myoglobin. The intact proteins and resulting peptides were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Centrifugation greatly improved the tryptic digestion efficiency of cytochrome c, where either an increase in centrifugation speed or in digestion duration significantly improved the digestion of cytochrome c. However, centrifugation did not noticeably improve the digestion of myoglobin; 16 h of centrifuge-assisted tryptic digestion at $30,000{\times}g$ barely removed the myoglobin protein peak. Similar results were also obtained when using conventional tryptic digestion with gentle mixing. When acetonitrile (ACN) was added to make 10% ACN buffer solutions, the myoglobin protein peak disappeared after 6 h of digestion using both centrifuge-assisted and conventional tryptic digestions.

Bacterial analysis by laser desorption ionization mass spectrometry on amorphous silicon

Kim, Shin Hye,Kim, Jeongkwon,Jo, Seung-Hyun,Kim, Jeong-Hoon,Kim, Kyung Joong,Yoon, Sohee American Institute of Physics 2016 Biointerphases Vol.11 No.4

<P>Lipid profiling in nine bacterial species has been accomplished by laser desorption ionization mass spectrometry (LDI-MS) using amorphous silicon (a-Si) thin film with 100 nm thickness. Lipid ions could be generated by LDI on a-Si regardless of ion acquisition modes because of a thermal property of a-Si to govern laser-induced surface heating. In a comparative study of lipid profiling in Bacillus lichemiformis by LDI-MS and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), LDI-MS on a-Si shows a higher efficiency in lipid and lipopeptide detection than MALDI-MS. A total of 53 peaks of lipid ions generated by LDI on a-Si in both acquisition modes for m/z 400-1200 was 1.6 times more than that detected by MALDI-MS using three organic matrices-2,5-dihydroxybenzoic acid, 1,5-diaminonaphthalene, and 2,4,6-trihydroxyacetophenone monohydrate. Also, the authors demonstrate by mass spectrometry imaging (MSI) that LDI-MS provides high detection coverage through whole sample area. MSI results show the detection yield in LDI on a-Si is 94.8% calculated by counting the number of points detected in the analyte ion signal in a whole spot. It means that reproducible detection of lipid ions by LDI-MS is possible even if laser is randomly irradiated at any position within the bacterial sample area applied on a-Si. Lipid profiling by LDI-MS on a-Si was applied to bacterial differentiation of nine bacterial species conducted by performing principal component analysis. Nine bacterial species are successfully distinguishable from each other by LDI-MS lipid profiling. (C) 2016 American Vacuum Society.</P>

Microwave-Assisted Protein Digestion in a Plate Well for Facile Sampling and Rapid Digestion

Kim, Hyeonil,Kim, Han Sol,Lee, Dabin,Shin, Dongwon,Shin, Daeho,Kim, Jeongkwon,Kim, Jungbae American Chemical Society 2017 ANALYTICAL CHEMISTRY - Vol.89 No.20

<P>Protein digestion is one of the most important processes in proteomic analysis. Here, we report microwave-assisted protein digestion in a plate well, which allows for facile sampling as well as rapid protein digestion based on the combination of highly stable enzyme immobilization and 3D printing technologies. Trypsin (TR) was immobilized on polystyrene-based nanofibers via an enzyme coating (EC) approach. The EC with stabilized TR activity was assembled with the 3D-printed structure in the plate well (EC/3D), which provides two separated compartments for the solution sampling and the TR-catalyzed protein digestion, respectively. EC/3D can effectively prevent the interference of sampling by accommodating EC in the separated compartment from the sampling hole in the middle. EC/3D in the plate well maintained its protein digestion performance under shaking over 160 days. Microwave irradiation enabled the digestion of bovine serum albumin within 10 min, generating the MALDI-TOF MS results of 75.0% sequence coverage and 61 identified peptides. EC/3D maintained its protein digestion performance under microwave irradiation after 30 times of recycled uses. EC/3D in the plate well has demonstrated its potential as a robust and facile tool for the development of an automated protein digestion platform. The combination of stable immobilized enzymes and 3D-printed structures can be potentially utilized not only for the protein digestion, but also for many other enzyme applications, including bioconversion and biosensors.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2017/ancham.2017.89.issue-20/acs.analchem.7b02169/production/images/medium/ac-2017-02169j_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac7b02169'>ACS Electronic Supporting Info</A></P>

Effect of centrifugation on tryptic protein digestion

Soohwan Kim,Yeoseon Kim,Dabin Lee,Inyoung Kim,Jihyun Paek,Dongwon Shin,Jeongkwon Kim 한국분석과학회 2017 분석과학 Vol.30 No.2

Sample Preparation of Corn Seed Tissue to Prevent Analyte Relocations for Mass Spectrometry Imaging

Kim, Shin Hye,Kim, Jeongkwon,Lee, Young Jin,Lee, Tae Geol,Yoon, Sohee Springer US 2017 Journal of the American Society for Mass Spectrome Vol.28 No.8

<P>Corn seed tissue sections were prepared by the tape support method using an adhesive tape, and mass spectrometry imaging (MSI) was performed. The effect of heat generated during sample preparation was investigated by time-of-flight secondary mass spectrometry (TOF-SIMS) imaging of corn seed tissue prepared by the tape support and the thaw-mounted methods. Unlike thaw-mounted sample preparation, the tape support method does not cause imaging distortion because of the absence of heat, which can cause migration of the analytes on the sample. By applying the tape-support method, the corn seed tissue was prepared without structural damage and MSI with accurate spatial information of analytes was successfully performed.</P> [FIG OMISSION]</BR>

Sample Preparation for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Kim, Jeongkwon Korean Society for Mass Spectrometry 2015 Mass spectrometry letters Vol.6 No.2

This article reviews the fundamentals of sample preparation used in matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). MALDI is a soft ionization method used to generate analyte ions in their intact forms, which are then detected in MS analysis. MALDI-MS boasts fast analysis times and easy-to-use operation. The disadvantages of MALDI-MS include the occurrence of matrix-associated peaks and inhomogeneous distribution of analyte within the matrix. To overcome the disadvantages of MALDI-MS, various efforts have been directed such as using different matrices, novel matrix systems, various additives, and different sample preparation methods. These various efforts will be discussed in detail. This article will benefit those who would like to obtain basic knowledge of MALDI sample preparation and those who would like to use MALDI-MS in their chemical analyses.

Effect of laser intensity on the apparent isotope patterns of heme and peptide ions in MALDI-TOF MS

Kim, Taehee,Lee, Jihyeon,Kim, Jeongkwon Elsevier 2015 INTERNATIONAL JOURNAL OF MASS SPECTROMETRY Vol.376 No.-

<P><B>Abstract</B></P> <P>The apparent isotope patterns of heme ions and tryptically digested peptide ions in matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF) mass spectra (MS) were systematically investigated as a function of laser intensity. Two standard proteins, myoglobin and cytochrome c, were tryptically digested to provide heme b and heme c ions, respectively, along with several peptides. MALDI mass spectra of these materials, co-deposited with one of two matrix materials, 2,5-dihydroxybenzoic acid or α-cyano-4-hydroxycinnamic acid (CHCA), were then generated using various laser intensities. For most peptides, the relative abundance of the second isotopic peak (SIP) to that of the monoisotopic peak was similar to the theoretical relative abundances. Regardless of laser intensity, the experimental SIP abundances of heme ions were consistently higher than the theoretical SIP abundances, which is due to the overlap of isobaric species. A gradual increase in the relative SIP abundance of the heme c ion was observed within a certain laser intensity range when the CHCA matrix was used with higher loadings (80pmol) of tryptically digested cytochrome c, which is likely due to saturation of the MALDI-TOF MS detector.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Isotopic distributions of heme and peptide ions in MALDI-MS analysis were comprehensively investigated as a function of laser intensity. </LI> <LI> For most peptides, the relative abundance of the second isotopic peak was similar to the theoretical relative abundances. </LI> <LI> The experimental abundances of the second isotopic peak of heme ions were consistently higher than the theoretical abundances, due to the overlap of isobaric species. </LI> <LI> Saturation of the MALDI-TOF MS detector was observed in a certain laser intensity range with higher loadings (80pmol) of tryptically digested cytochrome c using the CHCA matrix. </LI> </UL> </P>

Effect of Microwave Irradiation Time on Microwave-Assisted Weak Acid Protein Hydrolysis

Kim, Dahee,Joo, Minhee,Lee, Dabin,Nguyen, Huu-Quang,Kim, Jeongkwon Korean Society for Mass Spectrometry 2019 Mass spectrometry letters Vol.10 No.3

Horse heart myoglobin (MYG) and bovine serum albumin (BSA) were hydrolyzed by microwave-assisted weak-acid hydrolysis for 10, 20, 30, 40, 50, and 60 min using 2% formic acid (FA) at $100^{\circ}C$. Generally, the number of identified peptides increased with increasing irradiation time, indicating that the duration of microwave irradiation is linked to the efficiency of hydrolysis. For MYG, irradiation for 60 min provided the highest number of identified peptides, the greatest sequence coverage values and the highest MASCOT score values among the investigated irradiation times. Irradiation of BSA for 50 min, however, yielded a greater number of peptides than irradiation for 60 min due to the generation of miscleaved peptides after microwave irradiation for 50 min.

Commercial Silicon-on-Insulator (SOI) Wafers as a Versatile Substrate for Laser Desorption/Ionization Mass Spectrometry

Kim, Shin Hye,Kim, Jeongkwon,Moon, Dae Won,Han, Sang Yun Springer-Verlag 2013 Journal of the American Society for Mass Spectrome Vol.24 No.1

<P>We report here that a commercial silicon-on-insulator (SOI) wafer offers an opportunity for laser desorption/ionization (LDI) of peptide molecules, which occurs directly from its flat surface without requiring special surface preparation. The LDI-on-SOI exhibits intact ionization of peptides with a good detection limit of lower than 20 fmol, of which the mass range is demonstrated up to insulin with citric acid additives. The LDI process most likely arises from laser-induced surface heating promoted by two-dimensional thermal confinement in the thin Si surface layer of the SOI wafer. As a consequence of the thermal process, the LDI-on-SOI method is also capable of creating post-source decay (PSD) of the resulting peptide LDI ions, which is suitable for peptide sequencing using conventional TOF/TOF mass spectrometry.</P> [FIG OMISSION]</BR>