ORCID Profile
0000-0003-2270-5725
Current Organisations
Cargill (United States)
,
Monash University
,
Dartmouth College
,
Wake Forest Baptist Medical Center
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Publisher: Wiley
Date: 06-2015
DOI: 10.1002/BMC.3503
Abstract: Multivariate analysis of thin-layer chromatography (TLC) images was modeled to predict antioxidant activity of Pereskia bleo leaves and to identify the contributing compounds of the activity. TLC was developed in optimized mobile phase using the 'PRISMA' optimization method and the image was then converted to wavelet signals and imported for multivariate analysis. An orthogonal partial least square (OPLS) model was developed consisting of a wavelet-converted TLC image and 2,2-diphynyl-picrylhydrazyl free radical scavenging activity of 24 different preparations of P. bleo as the x- and y-variables, respectively. The quality of the constructed OPLS model (1 + 1 + 0) with one predictive and one orthogonal component was evaluated by internal and external validity tests. The validated model was then used to identify the contributing spot from the TLC plate that was then analyzed by GC-MS after trimethylsilyl derivatization. Glycerol and amine compounds were mainly found to contribute to the antioxidant activity of the s le. An alternative method to predict the antioxidant activity of a new s le of P. bleo leaves has been developed.
Publisher: Informa UK Limited
Date: 03-07-2014
Publisher: American Chemical Society (ACS)
Date: 29-08-2016
DOI: 10.1021/ACS.ANALCHEM.6B02017
Abstract: The experimental approach and mechanism of pressure tuning (PT) are introduced for the first stage of a comprehensive two-dimensional gas chromatography (GC × GC) separation. The PT-GC × GC system incorporates a first dimension ((1)D) coupled column ensemble comprising a pair of (1)D columns ((1)D1 and (1)D2) connected via a microfluidic splitter device, allowing variable decompression of carrier gas across each (1)D column, and a conventional (2)D narrow bore column. By variation of junction pressure between the (1)D1 and (1)D2 columns, tunable total (1)D retentions of analytes are readily derived. Separations of a standard mixture comprising a number of different chemical classes (including alkanes, monoaromatics, alcohols, aldehydes, ketones, and esters) and Australian tea tree oil (TTO) were studied as practical ex les of the PT-GC × GC system application. This illustrated the change of analyte retention time with experimental conditions depending on void time and retention on the different columns. In addition to void time change, variation of carrier gas relative decompression in the (1)D ensemble leads to tunable contribution of the (1)D1/(1)D2 columns that changes apparent polarity and selectivity of the ensemble. The resulting changes in (1)D elution order further altered elution temperature and thus retention of each analyte on the (2)D column in temperature-programmed GC × GC. 2D orthogonality measurements were then conducted to evaluate overall separation performance under application of different (1)D junction pressure. As a result, distribution and selectivity of particular target compounds, monoterpenes, sesquiterpenes, and oxygenated terpenes in 2D space, and thus orthogonality, could be adequately tuned. This indicates the potential of PT-GC × GC to be applicable for practical s le separation and provides a general approach to tune selectivity of target compounds.
Publisher: Elsevier BV
Date: 11-2014
Publisher: Elsevier BV
Date: 11-2014
Publisher: Cold Spring Harbor Laboratory
Date: 30-06-2021
DOI: 10.1101/2021.06.23.21259399
Abstract: Insulin Resistance (IR) affects a quarter of the world’s adult population and is a major factor in the pathogenesis of cardio-metabolic disease. Non-invasive s ling of exhaled breath contains metabolic markers indicative of underlying systemic metabolic abnormality. In this pilot study, we implemented a non-invasive breathomics approach, combined with random forest machine learning, to investigate metabolic markers from pre-diabetic Hispanic adolescents with obesity as indicators of abnormal metabolic regulation. Exhaled breath collection using the ReCIVA breathalyzer is feasible in an adolescent population. We have identified a signature of breath metabolites (breath-IR model) which correlates with Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) (R = 0.95, p .001). A strong correlation was also observed between the breath-IR model and the blood glycemic profile (fasting insulin R=0.91, p .001 and fasting glucose R=0.80, p .001). Among tentatively identified metabolites, limonene, undecane, and 2,7-dimethyl-undecane, significantly cluster in iduals based on HOMA-IR ( p =0.003, p =0.002, and p .001, respectively). Our breath-IR model differentiates between adolescents with and without IR with an area under the receiver operating characteristic curve of 0.87, after cross-validation. Identification of a breath metabolite signature indicative of IR in prediabetic Hispanic adolescents with obesity provides evidence of the utility of exhaled breath metabolomics for assessing systemic metabolic dysregulation. A simple and non-invasive breath-based test has utility as a diagnostic tool for monitoring IR progression, potentially allowing for earlier detection of IR and implementation of early interventions to prevent onset of type 2 diabetes mellitus. This study was funded by The Healthy Babies Project, Texas Biomedical Research Institute, San Antonio, TX.
Publisher: MDPI AG
Date: 03-06-2021
DOI: 10.3390/MICROORGANISMS9061211
Abstract: The current outbreak caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), termed coronavirus disease 2019 (COVID-19), has generated a notable challenge for diabetic patients. Overall, people with diabetes have a higher risk of developing different infectious diseases and demonstrate increased mortality. Type 2 diabetes mellitus (T2DM) is a significant risk factor for COVID-19 progression and its severity, poor prognosis, and increased mortality. How diabetes contributes to COVID-19 severity is unclear however, it may be correlated with the effects of hyperglycemia on systemic inflammatory responses and immune system dysfunction. Using the envelope spike glycoprotein SARS-CoV-2, COVID-19 binds to angiotensin-converting enzyme 2 (ACE2) receptors, a key protein expressed in metabolic organs and tissues such as pancreatic islets. Therefore, it has been suggested that diabetic patients are more susceptible to severe SARS-CoV-2 infections, as glucose metabolism impairments complicate the pathophysiology of COVID-19 disease in these patients. In this review, we provide insight into the COVID-19 disease complications relevant to diabetes and try to focus on the present data and growing concepts surrounding SARS-CoV-2 infections in T2DM patients.
Publisher: Elsevier BV
Date: 07-2016
DOI: 10.1016/J.CHROMA.2016.05.092
Abstract: The differential pressure drop of carrier gas by tuning the junction point pressure of a coupled column gas chromatographic system leads to a unique selectivity of the overall separation, which can be tested using a mixture of compounds with a wide range of polarity. This study demonstrates a pressure tuning (PT) GC system employing a microfluidic Deans switch located at the mid-point of the two capillary columns. This PT system allowed variations of inlet-outlet pressure differences of the two columns in a range of 52-17psi for the upstream column and 31-11psi for the downstream column. Peak shifting (differential migration) of compounds due to PT difference are related to a first order regression equation in a Plackett-Burman factorial study. Increased first (upstream) column pressure drop makes the second column characteristics more significant in the coupled column retention behavior, and conversely increased second (downstream) column pressure drop makes the first column characteristics more apparent such variation can result in component swapping between polar and non-polar compounds. The coupled column system selectivity was evaluated in terms of linear solvation energy relationship (LSER) parameters, and their relation with different pressure drop effects has been constructed by applying multivariate principle component analysis (PCA). It has been found that the coupled column PT system descriptors provide a result that shows a clear clustering of different pressure settings, somewhat intermediate between those of the two commercial columns. This is equivalent to that obtained from a conventional single-column GC analysis where the interaction energy contributed from the stationary phases can be significantly adjusted by choice of midpoint PT. This result provides a foundation for pressure differentiation for selectivity enhancement.
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.CHROMA.2017.10.060
Abstract: A pressure tunable (PT) coupled column ensemble has been implemented for the second dimension (
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 03-2014
Publisher: Elsevier BV
Date: 08-2013
Publisher: Elsevier BV
Date: 09-2016
Publisher: Elsevier BV
Date: 12-2014
Publisher: Elsevier BV
Date: 08-2013
Publisher: Elsevier BV
Date: 2014
Publisher: Bentham Science Publishers Ltd.
Date: 26-11-2020
DOI: 10.2174/2213240607999200813195405
Abstract: Green separation science involves extraction, pre-concentration and chromatographic analysis aiming at minimizing environmental impact by reducing energy and reagent usage and reducing or eliminating waste generation. However, the enrichment of trace analytes and/or the analysis of complex matrices most frequently require several steps before analysis, such as extraction, pre-concentration, clean up and preparative chromatography. Thus, alternative and greener separation techniques and solvents are replacing classical methods to diminish the carbon footprint and increase sustainability. Moreover, many innovations are also emerging to curtail the environmental impact of s les analysis such as micro or nano analytical platforms, sensor-based systems and direct injection to high-resolution mass spectrometry. The current review provides an updated account of the green and sustainable separation science techniques. The current innovations on greener separations and their application in different fields of study are discussed.
Location: No location found
Location: United States of America
No related grants have been discovered for Mohammad Sharif Khan.