Browsing by Author "Rahul Arya"

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Guanidine hydrochloride and urea-induced unfolding of Brugia malayi hexokinase
(2010) Alok Ranjan Singh; Shweta Joshi; Rahul Arya; Arvind Mohan Kayastha; Jitendra Kumar Saxena
Guanidine hydrochloride and urea-induced unfolding of B. malayi hexokinase (BmHk), a tetrameric protein, was examined in detail by using various optical spectroscopic techniques, enzymatic activity measurements, and size-exclusion chromatography. The equilibrium unfolding of BmHk by guanidine hydrochloride (GdmCl) and urea proceeded through stabilization of several unique oligomeric intermediates. In the presence of low concentrations of GdmCl, stabilization of an enzymatically active folded dimer of BmHk was observed. However an enzymatically inactive dimer of BmHk was observed for urea-treated BmHk. This is the first report of an enzymatically active dimer of hexokinase from any human filarial parasite. Furthermore, although complete recovery of the native enzyme was observed on refolding of BmHk samples denatured by use of low concentrations of GdmCl or urea, no recovery of the native enzyme was observed for BmHk samples denatured by use of high concentrations of GdmCl or urea. © 2009 European Biophysical Societies' Association.
Microplastics in the Atmosphere: Identification, Sources and Transport Pathways
(CRC Press, 2024) Rahul Arya; Jaswant Rathore; Ajay Kumar Mishra; Arnab Mondal
Microplastic (MP) pollution is a rising concern due to the overexploitation of plastics and absence of systematic dumping of plastic residue. The size of plastic particles ranging below 5 mm are termed as microplastics. Initial investigations focused on the effects of microplastic pollutants on marine as well as terrestrial ecosystems; however, recent studies have drawn attention to their presence in the atmosphere. The existence of fragmented plastics in the air was first reported in 2016, and thereafter, they were reported to be found in multiple studies conducted various environments, both indoor and outdoor conditions. The deficiency of data and lack of knowledge about their presence can be accredited to their prompt and long-range transport, which is aided by their smaller size. The current challenges with dearth of standard sampling procedures and detection approaches have limited the number of studies on airborne microplastic pollutants. Therefore, there exist large gaps in knowledge about their occurrence, horizontal and vertical distribution and their impact on air quality, ecosystem and human life. This chapter attempts to provide a broad illustration of current state of knowledge regarding atmospheric microplastics. In this chapter, we have attempted to provide an insight into microplastics in the atmosphere, its sources, types, transport pathways and an overview of the present measurement techniques along with its impacts. © 2024 selection and editorial matter, Surajit Mondal, Papita Das, Arnab Mondal, Subhankar Paul, Jitendra Kumar Pandey and Tapas K. Das. All rights reserved..
Molecular cloning and characterization of Brugia malayi hexokinase
(2008) Alok Ranjan Singh; Shweta Joshi; Rahul Arya; Arvind Mohan Kayastha; Kishore Kumar Srivastava; Lalit Mohan Tripathi; Jitendra Kumar Saxena
5′ EST from filarial gene database has been subjected to 3′ rapid amplification of cDNA ends (RACE), semi-nested PCR and PCR to obtain full-length cDNA of Brugia malayi. Full-length hexokinase gene was obtained from cDNA using gene specific primers. The elicited PCR product was cloned, sequenced and expressed as an active enzyme in Escherichia coli. Sequence analysis of B. malayi hexokinase (BmHk) revealed 59% identity with nematode Caenorhabditis elegans but low similarity with all other available hexokinases including human. BmHk, an apparent tetramer with subunit molecular mass of 72 kDa, was able to phosphorylate glucose, fructose, mannose, maltose and galactose. The Km values for glucose, fructose and ATP were found to be 0.035 ± 0.005, 75 ± 0.3 and 1.09 ± 0.5 mM respectively. BmHk was strongly inhibited by ADP, glucosamine, N-acetyl glucosamine and mannoheptulose. The recombinant enzyme was found to be activated by glucose-6-phosphate. ADP exhibited noncompetitive inhibition with the substrate glucose (Ki = 0.55 mM) while, mixed type of inhibition was observed with inorganic pyrophosphate (PPi) when ATP was used as substrate (Ki = 9.92 μM). The enzyme activity is highly dependent on maintenance of free sulfhydryl groups. CD analysis indicated that BmHk is composed of 37% α-helices and 26% β-sheets. The observed differences in kinetic properties of BmHk as compared to host enzyme may facilitate designing of specific inhibitors against BmHk. © 2008 Elsevier Ireland Ltd. All rights reserved.