North Eastern Hill University

About: North Eastern Hill University is a education organization based out in Shillong, Meghalaya, India. It is known for research contribution in the topics: Population & Catalysis. The organization has 2318 authors who have published 4476 publications receiving 48894 citations.

Effect of solvent hydrogen bonding on excited-state properties of luminol: a combined fluorescence and DFT study.

Abstract: The effect of solvent on the photoluminescence behavior of luminol was studied by steady-state fluorescence spectroscopy. The fluorescence spectral behavior of luminol is markedly different in polar protic solvents compared to that in aprotic solvents. A quantitative estimation of the contribution from different solvatochromic parameters, like solvent polarizibility (π*), hydrogen-bond donor (α), and hydrogen-bond acceptor (β), was made using the linear free energy relationship based on the Kamlet−Taft equation. The analysis reveals that the hydrogen-bond-donating ability (acidity) of the solvent is the most important parameter to characterize the excited-state behavior of luminol. Quantum mechanical calculations using density functional theory (DFT) predict the most stable structure, out of several possible tautomeric conformers of luminol with varying degrees of hydration. In the excited state, charge localization at specific points of the luminol phthalhydrazide moiety causes the solvent to interact pr...

Targeting the heme protein hemoglobin by (-)-epigallocatechin gallate and the study of polyphenol-protein association using multi-spectroscopic and computational methods.

Abstract: In this work, the interaction of a bioactive tea polyphenol (-)-epigallocatechin gallate (EGCG) with bovine hemoglobin (BHb) along with its anti-oxidative behavior and the anti-glycation property have been explored using multi-spectroscopic and computational techniques. The binding affinity for EGCG towards BHb was observed to be moderate in nature with an order of 104 M-1, and the fluorescence quenching mechanism was characterized by an unusual static quenching mechanism. The binding constant (Kb) showed a continuous enhancement with temperature from 3.468 ± 0.380 × 104 M-1 at 288 K to 6.017 ± 0.601 × 104 M-1 at 310 K. The fluorescence emission measurements along with molecular docking studies indicated that EGCG binds near the most dominant fluorophore of BHb (β2-Trp37, at the interface of α1 and β2 chains) within the pocket formed by the α1, α2 and β2 chains. The sign and magnitude of the thermodynamic parameters, changes in enthalpy (ΔH = +17.004 ± 1.007 kJ mol-1) and in entropy (ΔS = +146.213 ± 2.390 J K-1 mol-1), indicate that hydrophobic forces play a major role in stabilizing the BHb-EGCG complex. The micro-environment around the EGCG binding site showed an increase in hydrophobicity upon ligand binding. The binding of EGCG with BHb leads to a decrease in the α-helical content, whereas that of the β-sheet increased. FTIR studies also indicated that the secondary structure of BHb changed upon binding with EGCG, along with providing further support for the presence of hydrophobic forces in the complexation process. Molecular docking studies indicated that EGCG binds within the cavity of α1, α2, and β2 chains surrounded by residues such as α1- Lys99, α1-Thr134, α1-Thr137, α1-Tyr140, α2-Lys127 and β2-Trp37. Molecular dynamics simulation studies indicated that EGCG conferred additional stability to BHb. Furthermore, moving away from the binding studies, EGCG was found to prevent the glyoxal (GO)-mediated glycation process of BHb, and it was also found to act as a potent antioxidant against the photo-oxidative damage of BHb.

Population dynamics of Eupatorium adenophorum Spreng. during secondary succession after slash and burn agriculture (jhum) in north eastern India

Abstract: Summary Eupatorium adenophorum Spreng. is an important weedy colonizer in early successional communities developing after slash and burn agriculture (jhum) at higher elevations of the north-eastern hill regions of India. The relative performance of this species in terms of fecundity and survivorship in successional plant communities has been worked out. A net population increase occurred through both vegetative and sexual reproduction in early successional fallows up to 6 years old, the increase being greatest in a 6-year fallow. Mortality of seedlings was high in 1- and 3-year fallows, low in a 6-year fallow but reached 100% in older fallows. Seedling mortality was maximal during the monsoon although some seedlings also died during winter as a result of drought and frost. Mortality of vegetative sprouts followed a similar pattern to that of seedlings. The reproductive potential was reduced with increasing age of the successional communities and in a 15-year fallow all individuals were non-reproductive. Since E. adenophorum is able to succeed only in fallows of less than 6 years, repeated short jhum cycles of 4–5 years have had the effect of arresting succession al the weedy stage. Resume La dynamique des populations de Eupatorium adenophorum Spreng. se developpant apres abattage et brulage (jhum) dans le nord-est de l'Inde Eupatorium adenophorum Spreng. est une mauvaise herbe qui colonise de facon importante les surfaces ou ont ete pratiques l'abattage et le brulage (jhum) sur les sommets les plus eleves des regions montagneuses du nord-est de l'Inde. Les performances de cette espece en terme de fecondite et d'aptitude au developpement ont eteetudiees dans des successions de communautes botaniques. Un developpement net de la population s'est produit par la multiplication vegetative et sexuee des la mise en jachere et pendant une periode de 6 ans, le developpement de la population etant le plus important la 6eme annee. La mortalite des plantules etait elevee dans la premiere et la 3eme annee. mais basse la 6eme annee: dans des jacheres plus anciennes, ellc pouvait atteindre 100%. Cette disparition des plantules etait maximale durant la mousson, bien que quelques individus aient disparu egalement durant I'hiver en raison du gel et de la secheresse. La mortalite des rejets aeriens a suivi le meme schema. Le potentiel de reproduction etait reduite an fur el a mesure que les communautes vieillissaient et. dans une jachere de 15 ans. tous les individus etaient steriles. En raison de l'aptitude de Eupatorium adenophorum Spreng. a se developper seulement dans des jacheres de moinsde 6 ans. des cycles courts repetes de jhum (4–5 ans) ont eu pour effet d'arreter le developpement des mauvaises herbes. Zusammenfassung Populationsdynamik von Eupatorium adenophorum Spreng. wahrend der sekundaren Sukzession nach Hack- und Brandfeldbau (Jhum) im Nordosten Indiens Eupalorium adenophorum Spreng. ist eine hedeu-tende Besiedlungspflanze in den ersten Sukzes-sionsgesellschaften nach Hack- und Brandfeld-bau (Jhum) in den hoheren Regionen der nor-dostlichen Berggebiete Indiens. Das Verhalten dieser Art hinsichtlich Fruchtbarkeit und Uberle-bensrate in Sukzessionsfolgen wurde erarbeitet. Die Population vermehrte sich sowohl vegetativ wie sexuell in den ersten bis zu 6 Jahre alten Sukzessionsbrachen. wobei die grosste Zunahme in einer sechsjahrigen Brache zu verzeichnen war. Die Keimlingsmortalitat war in den ein- und dreijiihrigen Brachen hoch und in einer sechsjah-rigen Brache niedrig; in iiiteren Brachen hetrug sie aber bis zu 100%. Die Keimlingsmortalitat war wahrend der Monsunzeit am hochsten. einige Keimlinge starben aber auch im Winter durch Trockenheit und Frost. Die Mortalitiit vegetativ gebildeter Sprosse entsprach in etwa dem der Keimlinge. Das Vermehrungspotential nahm mit zunehmendem Alter der Pflanzengesellschaften ab und in einer 15jahrigen Brache waren alle Individuen nicht mehr vermehrungsfahig. Da E. adenophorum sich nur in Brachen. die nicht alter als 6 Jahre sind weiterentwickeln kann. bewirkten 4–5jahrige Jhum-Folgen, dass die Flachen mit dieser Art verunkrautet blieben.