Elucidating H/D-Exchange Mechanism of Active Hydrogen in Aniline and Benzene-1,2-dithiol

( Arif Ahmed ),( Syful Islam ),( Sunghwan Kim ) 한국질량분석학회 2021 Mass spectrometry letters Vol.12 No.4

In this study, the hydrogen/deuterium (HDX) exchange mechanism of active hydrogen, nitrogen, and sulfur-containing polycyclic aromatic hydrocarbon (PAH) dissolved in toluene and deuterated methanol by atmospheric pressure photoionization (APPI) is investigated. The comparison of the data obtained using APPI suggests that aniline and benzene-1,2-dithiol contain two exchanging hydrogens. The APPI HDX that best explains the experimental findings was investigated with the use of quantum mechanical calculations. The HDX mechanism is composed of a two-step reaction: in the first step, analyte radical ion gets deuterated, and in the second step, the hydrogen transfer occurs from deuterated analyte to de-deuterated methanol to complete the exchange reaction. The suggested mechanism provides fundamentals for the HDX technique that is important for structural identification with mass spectrometry. This paper is dedicated to Professor Seung Koo Shin for his outstanding contributions in chemistry and mass spectrometry.

Elucidating Molecular Structures of Nonalkylated and Short-Chain Alkyl (<i>n</i> < 5, (CH₂)_<i>n</i>) Aromatic Compounds in Crude Oils by a Combination of Ion Mobility and Ultrahigh-Resolution Mass Spectrometries and Theoretical Coll

Ahmed, Arif,Cho, Yunju,Giles, Kevin,Riches, Eleanor,Lee, Jong Wha,Kim, Hugh I.,Choi, Cheol Ho,Kim, Sunghwan American Chemical Society 2014 ANALYTICAL CHEMISTRY - Vol.86 No.7

<P>Ultrahigh-resolution mass spectrometry has allowed the determination of elemental formulas of the compounds comprising crude oils. However, elucidating molecular structures remains an analytical challenge. Herein, we propose and demonstrate an approach combining ion mobility mass spectrometry (IM-MS), ultrahigh-resolution mass spectrometry, and theoretical collisional cross-section (CCS) calculations to determine the molecular structures of aromatic compounds found in crude oils. The approach is composed of three steps. First, chemical structures are suggested based on the elemental formulas determined from ultrahigh-resolution mass spectra. Second, theoretical CCS values are calculated based on these proposed structures. Third, the calculated CCS values of the proposed structures are compared with experimentally determined CCS values from IM-MS data to provide proposed structures. For proof of concept, 31 nonalkylated and short-chain alkyl (<I>n</I> < 5, (CH<SUB>2</SUB>)<SUB><I>n</I></SUB>) aromatic compounds commonly observed in crude oils were analyzed. Theoretical and experimental CCS values matched within a 5% RMS error. This approach was then used to propose structures of compounds in selected <I>m</I>/<I>z</I> regions of crude oil samples. Overall, the combination of ion mobility mass spectrometry, ultrahigh-resolution mass spectrometry, and theoretical calculations was shown to be a useful tool for elucidating chemical structures of compounds in complex mixtures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2014/ancham.2014.86.issue-7/ac4032737/production/images/medium/ac-2013-032737_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac4032737'>ACS Electronic Supporting Info</A></P>

Systematic Investigation into the Differences in the (+) APPI Efficiencies of Positional (Ortho, Meta, and Para) Isomers

Arif Ahmed,Syful Islam,Nissa Nurfajrin Solihat,Thamina Acter,김성환 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.11

Understanding the underlying principle behind the ionization technique is important for improving the sensitivity and selectivity of mass spectrometry (MS), and analyte?solvent interactions are important factors that affect the ionization process. In this study, analyte?solvent interactions were investigated using a series of ortho, meta, and para isomers, (+) APPI-MS, and computational chemistry. Experimental results reveal that isomers can have vastly different ionization efficiencies, despite their identical elemental formulas and functional groups. To better understand the reasons behind these observations, various analyte?solvent radical-ion complexes were investigated by quantum mechanical techniques, and the factors that contribute to the differences in the ion-formation behavior of these compounds were thoroughly investigated.

Stable Ferroelectric Behavior of Nb-Modified Bi0.5K0.5TiO3-Bi(Mg0.5Ti0.5)O3 Lead-Free Relaxor Ferroelectric Ceramics

Zaman, Arif,Malik, Rizwan Ahmed,Maqbool, Adnan,Hussain, Ali,Ahmed, Tanveer,Song, Tae Kwon,Kim, Won-Jeong,Kim, Myong-Ho Minerals, Metals & Materials Society and the Insti 2018 Journal of electronic materials Vol.47 No.3

<P>Crystal structure, dielectric, ferroelectric, piezoelectric, and electric field-induced strain properties of lead-free Nb-modified 0.96Bi(0.5)K(0.5)TiO(3)-0.04Bi(Mg0.5Ti0.5)O-3 (BKT-BMT) piezoelectric ceramics were investigated. Crystal structure analysis showed a gradual phase transition from tetragonal to pseudocubic phase with increasing Nb content. The optimal piezoelectric property of small-signal d (33) was enhanced up to similar to 68 pC/N with a lower coercive field (E (c)) of similar to 22 kV/cm and an improved remnant polarization (P (r)) of similar to 13 mu C/cm(2) for x = 0.020. A relaxor-like behavior with a frequency-dependent Curie temperature T (m) was observed, and a high T (m) around 320A degrees C was obtained in the investigated system. This study suggests that the ferroelectric properties of BKT-BMT was significantly improved by means of Nb substitution. The possible shift of depolarization temperature T (d) toward high temperature T (m) may have triggered the spontaneous relaxor to ferroelectric phase transition with long-range ferroelectric order without any traces of a nonergodic relaxor state in contradiction with Bi0.5Na0.5TiO3-based systems. The possible enhancement in ferroelectric and piezoelectric properties near the critical composition x = 0.020 may be attributed to the increased anharmonicity of lattice vibrations which may facilitate the observed phase transition from a low-symmetry tetragonal to a high-symmetry cubic phase with a decrease in the lattice anisotropy of an undoped sample. This highly flexible (at a unit cell level) narrow compositional range triggers the enhancement of d (33) and P (r) values.</P>

Microsatellite Marker Based Screening and Bioassay to Select for Qualitative Resistance Against Leptosphaeria maculans in Cabbage (Brassica oleracea L.)

Arif Hasan Khan Robin,Jongin Park,Nasar Uddin Ahmed,Rawnak Laila,Ill-Sup Nou 한국원예학회 2015 한국원예학회 학술발표요지 Vol.2015 No.5

Existence of qualitative resistance against blackleg disease in Brassica oleracea L. and detection of gene-specific single nucleotide polymorphism

Arif Hasan Khan Robin,Jong-In Park,Nasar Uddin Ahmed,Rawnak Laila,Ill-Sup Nou 한국육종학회 2015 한국육종학회 심포지엄 Vol.2015 No.07

Blackleg disease caused by Leptosphaeria maculans, is the most devastating disease of Brassica germplam worldwide that causes million tonnes of crop losses per year throughout the world. To date, a total of 12 race-specific resistance genes of Brassica napus to L. maculans have been reported but linkage mapping analysis reveals that all of those loci are located in A genome i.e., in B. rapa chromosomes. B. oleracea has high ancestral synteny with B. rapa through their evolution. We believe that presence of qualitative resistance is possible in B. oleracea germplasm. The present study was therefore planned to find out any race-specific qualitative resistance gene present in C genome of B. oleracea. A total of 16 microsatellite markers were used which are linked to seven different Rlm and Lep genes of B. napus to screen 32 inbred lines of cabbage. Primers were designed based on homology assessment in corresponding nucleotide sequence available in Bolbase (a B. oleracea genome database, http://www.ocri-genomics.org/bolbase/index.html), located in B. oleracea scaffolds/chromosomes. Out of 16 SSR markers, 13 were found polymorphic which indicates possible existence of resistant genes in cabbage lines. The inbred lines are then assessed against two L. maculans stains with known avirulent genes. Some inbred lines were hypersensitive against gene-specific virulent strains of L. maculans that confirmed existence of Rlm1, Rlm2, Rlm4, LepR3 and LepR4 in the cabbage lines. In this way we were able to select out resistant and susceptible lines against each resistant gene. The gene-specific polymorphic SSR marker regions were cloned and sequenced and candidate SNPs were identified for confirmation of their functionality.

PE-106: Presence of Anemia Predicts Advanced Grade at Presentation in Patients with Hepatic Encephalopathy

( Nauman Arif Jadoon ),( Zeeshan Butt ),( Ahmed Shahzad ),( Kamran Mushtaq ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1

Aims: The objective of our study was to assess the impact of anemia on HE grade at presentation. Methods: Consecutive patients of HE admitted in the medical wards of Mayo Hospital, Lahore during March 2010 and May 2010 were enrolled in the study. HE grade at presentation was assessed by using West-Haven Criteria. Complete blood count, bleeding profile, liver function tests and ultrasound was done in emergency at presentation. Anemia was defined as hemoglobin level less than 12 g/dl. Univariate and multivariate logistic regression analysis was done to assess the impact of anemia on hepatic encephalopathy grade at presentation. P value <0.05 was considered significant. Results: 61 patients were included in the study. 20% patients were in grade 1 HE; 20% in grade 2; 39% in grade 3; and 21% in grade 4 HE. Advanced grade HE was defined as HE grade >2. On univariate analysis prothrombin time >15 seconds, diabetes, esophageal varices on endoscopy, and anemia were significant predictors of advanced grade HE (p values: 0.048, 0.048, 0.039, 0.037). Hypoalbuminemia was less common in advanced grade HE patients (p, 0.004). Child Pugh Score and MELD Score had no relation with HE grade at presentation. All the significant factors in univariate analysis were included in the multivariate logistic regression model. Only anemia was significant predictor of advanced grade HE in multivariate analysis (p, 0.018). Conclusions: Sixty percent of HE patients present with advanced grade. Anemia is associated with advanced HE grade at presentation.

Comparison of Theoretical Calculation Methods for Obtaining Collisional Cross-Section of Aromatic Compounds

임동완,Arif Ahmed,김성환 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.8

Flow chart of the comparison between experimental collisional cross-section (CCS) and theoretical CCS.

Use of Smoke-less Tobacco Amongst the Staff of Tertiary Care Hospitals in the Largest City of Pakistan

Valliani, Arif,Ahmed, Bilawal,Nanji, Kashmira,Valliani, Salimah,Zulfiqar, Beenish,Fakih, Misbah,Mehdi, Mehwish,Khan, Anam,Sheikh, Sana Arshad,Fatima, Nida,Ahmad, Sobia,Farah, Fariya,Saleem, Shaheera,A Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.5

Background: Use of smoke-less tobacco (SLT) is very common in South and South-East Asian countries. It is significantly associated with various types of cancers. The objectives of this study were to assess the proportion of hospital staff that use SLT, and to identify the factors associated with its use and their practices. Methods: In a cross-sectional study, 560 staff of two tertiary care hospitals were interviewed in the year 2009. Nurses, ward boys and technicians were counted as a paramedic staff while drivers, peons, security guards and housekeeping staff were labeled as non-paramedic staff. SLT use was considered as usage of any of the following: betel quid (paan) with or without tobacco, betel nuts with or without tobacco (gutkha) and snuff (naswar). Results: About half (48.6%) of the hospital staff were using at least one type of SLT. Factors found to be statistically significant with SLT were being a male (OR=2.5; 95% CI=1.8-3.7); having no/fewer years of education (OR=1.7; 95% CI=1.2-2.4) and working as non-paramedic staff (OR=2.6; 95% CI=1.8-3.8). Majority of SLT users were using it on regular basis, for > 5 years and keeping the tobacco products in the oral cavity for >30 minutes. About half of the users started due to peer pressure and had tried to quit this habit but failed. Conclusion: In this study, about half of the study participants were using SLT in different forms. We suggest educational and behavioral interventions for control of SLT usage.

PE-107: Hyponatremia in Decompens ated Cirrhosis: Is It Associated with More Severe Disease?

( Nauman Arif Jadoon ),( Zeeshan Butt ),( Ahmed Shahzad ),( Kamran Mushtaq ) 대한간학회 2016 춘·추계 학술대회 (KASL) Vol.2016 No.1

Aims: The aim of our study was to evaluate whether there is any association between hyponatremia and severity of decompensated cirrhosis. Methods: Consecutive patients of decompensated cirrhosis presenting at three tertiary care hospitals were included in the study. Hyponatremia was defined as serum sodium levels of <135 mEq/L. Patients with Child-Pugh Class A and B were considered having mild disease and Class C patients were categorized as having severe disease. Results: A total of 202 patients were included in the study with male preponderance (53%). Patients presenting with Child-Pugh Class A, B and C were 16 (6.9%), 74 (36.6%) and 114 (56.4%) respectively. Hyponatremia was present in 37.3% of the patients. On bivariate analysis, factors associated with severe decompensated cirrhosis (Child-Pugh Class C) were total protein <6 g/dL (p, 0.002), hemoglobin level <12 g/dL (p, 0.006), APTT >35 seconds (p <0.001), AST >35 IU (p, 0.03) and serum sodium level <135 mEq/L. Thrombocytopenia, raised blood urea, raised serum creatinine, and hyperkalemia were not associated with severity of decompensated cirrhosis as was the etiology of cirrhosis (Hepatitis C versus non-hepatisis C). Variables significant in the bivariate analysis were then included in the multivariate logistic regression model. All the variables remained significant except anemia which did not show any association with severity of disease in multivariate analysis. Conclusions: One third of the patients with decompensated cirrhosis in the present study had hyponatremia which was associated with less severe disease (lower Child-Pugh Class) at presentation.