University of Madras

About: University of Madras is a education organization based out in Chennai, Tamil Nadu, India. It is known for research contribution in the topics: Ring (chemistry) & Lipid peroxidation. The organization has 8496 authors who have published 11369 publications receiving 211152 citations. The organization is also known as: Madras University & University of Chennai.

Unravelling the Multiple Emissive States in Citric-Acid-Derived Carbon Dots

Abstract: Steady-state and time-resolved fluorescence spectroscopy techniques were used to probe multifluorescence resulting from citric-acid-derived carbon dots (C-dots). Commonly, both carboxyl-/amine-functionalized C-dots exhibit three distinct emissive states corresponding to the carbon-core and surface domain. The shorter-wavelength fluorescence (below 400 nm) originates from the carbon-core absorption band at ∼290 nm, whereas the fluorescence (above 400 nm) is caused by two surface states at ∼350 and 385 nm. In addition to three emissive states, a molecular state was also found in amine-functionalized C-dots. Time-resolved emission spectra (TRES) and time-resolved area normalized emission spectra (TRANES) were analyzed to confirm the origin of excitation wavelength-dependent fluorescence of C-dots. The surface functional groups on the C-dots are capable of regulating the electron transfer to affect the multifluorescence behavior. The electron transfer takes place from the carbon-core to surface domain by the ...

Coexistence of blaOXA-23 with blaNDM-1 and armA in clinical isolates of Acinetobacter baumannii from India.

Abstract: Sir, The production of carbapenemases is the most common mechanism responsible for carbapenem resistance in Acinetobacter baumannii. They include metallo-b-lactamases (VIM, IMP and SIM types), which have been sporadically reported in some parts of the world, and acquired OXA-type carbapenemases which have been more frequently identified worldwide and are clustered in three major subfamilies (blaOXA-23, blaOXA-24 and blaOXA-58). 1 High levels of resistance to aminoglycosides due to the production of plasmid-encoded 16S rRNA methylase in Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter spp. have been documented since 2003. The present study was undertaken to determine the mechanism responsible for the carbapenem resistance. Three carbapenem-non-susceptible A. baumannii were isolated from patients in the intensive care unit of a tertiary care hospital in Chennai, India in April 2010. Species identification and antibiotic testing were carried out using an automated machine (VITEK-2). The MICs of carbapenems and aminoglycosides were determined using the CLSI agar dilution method, while tigecycline MICs were determined using the EUCAST broth microdilution method. All the isolates were resistant to all the b-lactams, aminoglycosides and quinolones, and were only susceptible to tigecycline and colistin. Double disc synergy test (DDST) and modified Hodge test (MHT) were used for detection of metallo-b-lactamases and other carbapenemases, respectively. PCR screening was performed for OXA-type carbapenemases (blaOXA-23, -24, -51 and -58-like) and the known metallo-b-lactamase genes. 3 – 5 All three isolates showed positivity for both DDST and MHT, and PCR yielded the products with expected sizes for blaOXA-51, 23-like and blaNDM-1 (Table 1). Sequencing of both blaOXA-23 and blaNDM-1 genes showed 100% identities with previously reported genes. In all three isolates, the blaOXA-23 gene was adjacent to insertion element ISAba1, which provides the promoter required for expression of linked resistance genes; blaOXA-51-like genes were also found in all of the isolates, but were not activated by ISAba1. Conjugation experiments using Escherichia coli J53 as the recipient were unsuccessful. Plasmids of Enterobacteriaceae were not detected among A. baumannii by PCR-based replicon typing. Susceptibility testing showed increased MICs of carbapenems and an unusual phenotype of broad-spectrum high-level resistance to aminoglycosides, including amikacin, gentamicin, netilmicin and tobramycin (MICs.256 mg/L), with susceptibility to tigecycline (MIC1⁄40.5–1 mg/L). PCR screening was performed for 16S rRNA methylase-encoding genes (armA, rmtA, rmtB, rmtC, rmtD and npmA). – 9 All three isolates showed positivity for the armA gene (Table 1). NDM-1 metallo-b-lactamase-mediated resistance to carbapenems in Enterobacteriaceae has been found in many parts of India. However, to our knowledge, this is the first

Genetic Variation Among World Populations: Inferences From 100 Alu Insertion Polymorphisms

Abstract: We examine the distribution and structure of human genetic diversity for 710 individuals representing 31 populations from Africa, East Asia, Europe, and India using 100 Alu insertion polymorphisms from all 22 autosomes. Alu diversity is highest in Africans (0.349) and lowest in Europeans (0.297). Alu insertion frequency is lowest in Africans (0.463) and higher in Indians (0.544), E. Asians (0.557), and Europeans (0.559). Large genetic distances are observed among African populations and between African and non-African populations. The root of a neighbor-joining network is located closest to the African populations. These findings are consistent with an African origin of modern humans and with a bottleneck effect in the human populations that left Africa to colonize the rest of the world. Genetic distances among all pairs of populations show a significant product-moment correlation with geographic distances (r = 0.69, P < 0.00001). F(ST), the proportion of genetic diversity attributable to population subdivision is 0.141 for Africans/E. Asians/Europeans, 0.047 for E. Asians/Indians/Europeans, and 0.090 for all 31 populations. Resampling analyses show that approximately 50 Alu polymorphisms are sufficient to obtain accurate and reliable genetic distance estimates. These analyses also demonstrate that markers with higher F(ST) values have greater resolving power and produce more consistent genetic distance estimates.