02105nas a2200169 4500008004100000022001400041245010100055210006900156260007100225300001600296490000800312520141500320100002801735700002801763700002601791856011801817 2008 eng d a0002-786300aChanges in dynamics of SRE-RNA on binding to the VTS1p-SAM domain studied by C-13 NMR relaxation0 aChanges in dynamics of SRERNA on binding to the VTS1pSAM domain  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP a12007-120200 v1303 a

RNA recognition by proteins is often accompanied by significant changes in RNA dynamics in addition to conformational changes. However, there are very few studies which characterize the changes in molecular motions in RNA on protein binding. We present a quantitative C-13 NMR relaxation study of the changes in RNA dynamics in the pico-nanosecond time scale and micro-millisecond time scale resulting from interaction of the stem-loop SRE-RNA with the VTS1p-SAM domain. C-13 relaxation rates of the protonated carbons of the nucleotide base and anomeric carbons have been analyzed by employing the model-free formalism, for a fully C-13/N-15-labeled sample of the SRE-RNA in the free and protein-bound forms. In the free RNA, the nature of molecular motions are found to be distinctly different in the stem and the loop region. On binding to the protein, the nature of motions becomes more homogeneous throughout the RNA, with many residues showing increased flexibility at the aromatic carbon sites, while the anomeric carbon sites become more rigid. Surprisingly, we also observe indications of a slow collective motion of the RNA in the binding pocket of the protein. The observation of increased motions on binding is interesting in the context of growing evidence that binding does not always lead to motional restrictions and the resulting entropy gain could favor the free energy of association.

1 aOberstrass, Florian, C.1 aAllain, Frederic, H. T.1 aRavindranathan, Sapna uhttp://library.ncl.res.in/content/changes-dynamics-sre-rna-binding-vts1p-sam-domain-studied-c-13-nmr-relaxation-002565nas a2200193 4500008004100000245013000041210006900171260000800240300001600248490000700264520184300271100002702114700001902141700001602160700002402176700002602200700001702226856012802243 2017 eng d00aChiral discrimination through h-1 nmr and luminescence spectroscopy: dynamic processes and solid strip for chiral recognition0 aChiral discrimination through h1 nmr and luminescence spectrosco cDEC a18303-183130 v233 aThe appropriate choice of the host molecules with well-defined optical activity (S-H/R-H) helps in the differentiation between two secondary ammonium ion-derivative guest molecules with different optical activities (R-G/S-G) based on the fluorescence resonance energy transfer (FRET)based luminescence responses. Crown ether-based host molecules with opposite chiral configurations (R-H, S-H) have been derived from 1,1'-bi-2-naphthol (BINOL) derivatives that have axially chiral biaryl centers. These chiral crown ethers form host-guest complexes (i.e., [2] pseudoro-taxanes) with chiral secondary ammonium ion derivatives (R-G, S-G). NMR spectroscopic studies show that the complexes are in a dynamic equilibrium in solution. Results of the H-1 NMR and fluorescence spectroscopic studies indicate a head-on orientation of the host and guest in the [2] pseudorotaxanes. The difference in the efficiency in the FRET-based responses between anthracene and the BINOL derivatives allow efficient chiral discrimination of the guests. Isothermal titration calorimetry and NMR investigations reveal that inclusion complexes between hosts and guests of the same chirality (R-H center dot R-G, S-H center dot S-G) are more stable relative to those of opposite chirality (R-H center dot S-G, S-H center dot R-G). However, FRET-based energy-transfer efficiency is higher for R-H center dot S-G and S-H center dot R-G complexes. NMR spectroscopic studies show that the relative orientation of the guest in the host cavity is significantly different when the host binds a guest of the same or opposite chirality; furthermore, the latter is more favorable for FRET, thus enabling discrimination between enantiomers. Interestingly, chiral discrimination of guest ions could also be achieved by using silica surfaces modified with chiral host molecules.1 aGangopadhyay, Monalisa1 aMaity, Arunava1 aDey, Ananta1 aRajamohanan, P., R.1 aRavindranathan, Sapna1 aDas, Amitava uhttp://library.ncl.res.in/content/chiral-discrimination-through-h-1-nmr-and-luminescence-spectroscopy-dynamic-processes-and01920nas a2200193 4500008004100000245008100041210006900122260000800191300001600199490000700215520124900222100002101471700001901492700002701511700002601538700003501564700001701599856011001616 2017 eng d00aCucurbit[7]uril induced formation of fret-enabled unilamellar lipid vesicles0 aCucurbit7uril induced formation of fretenabled unilamellar lipid cOCT a10989-109990 v333 aA unique fluorescence resonance energy transfer (FRET) process is found to be operational in a unilamellar lipid self-assembly in the aqueous phase. A newly synthesized naphthyl based long chain lipid derivative [N-(naphthalene-1-ylmethyl)tetradecane-1-ammonium chloride, 14NA(+)] forms various self-assembled architectures in the aqueous phase. Controlled changes in lipid concentration lead to a transition of the self-assemblies from micelles to vesicles to rods. In the presence of cucurbit[7]uril (CB7), 14NA(+) forms a host-guest [2]pseudorotaxane complex (CB7(sic)14NA(+)) and secondary interactions lead to the formation of a lipid bilayer with hydrophobic pockets situated in between the layers. The change in the structure of 14NA(+) assemblies, interaction with CB7 and formation of supramolecular assemblies of CB7(sic)14NA(+) were examined using light scattering, spectroscopic, and microscopic techniques. Entrapment of a luminescent dye, anthracene within the hydrophobic bilayer of the supramolecular assembly CB7(sic)14NA(+) favors a modified luminescent response due to an efficient FRET process. Further, the FRET process could be controlled by thermal and chemical stimuli that induce transformation of unilamellar vesicles.1 aKushwaha, Shilpi1 aMaity, Arunava1 aGangopadhyay, Monalisa1 aRavindranathan, Sapna1 aRajamohanan, Pattuparambil, R.1 aDas, Amitava uhttp://library.ncl.res.in/content/cucurbit7uril-induced-formation-fret-enabled-unilamellar-lipid-vesicles02444nas a2200217 4500008004100000245009700041210006900138260000800207300001400215490000700229520166200236100003301898700000501931700001801936700003801954700002301992700002602015700003402041700003002075856012102105 2019 eng d00aCharge transfer liquid: a stable donor-acceptor interaction in the solvent-free liquid state0 aCharge transfer liquid a stable donoracceptor interaction in the cAUG a9371-93740 v553 a

Charge-transfer complexes have been an inspiration to develop many functional soft materials. However, most of those studies have focused on solution based assemblies wherein the explicit control of solvents and their polarity are crucial. In this context, we explore an efficient and stable charge transfer liquid using a solvent-free liquid dialkoxynaphthalene donor and a naphthalenediimide acceptor. It has been observed that irrespective of the donor-acceptor ratio, the charge-transfer liquid exhibited an unprecedented stability and retained characteristic features even at increased temperatures. The underlying intermolecular interactions leading to efficient CT have been examined by NMR techniques together with theoretical modelling studies. The concept of charge transfer liquid will be highly beneficial for the development of processable optoelectronically active materials.
 

1 aWakchaure, Vivek, Chandrakan1 a1 aGoudappagouda1 aRanjeesh, Kayaramkodath, Chandran1 aChakrabarty, Suman1 aRavindranathan, Sapna1 aRajamohanan, Pattuparambil, R1 aBabu, Sukumaran, Santhosh uhttp://library.ncl.res.in/content/charge-transfer-liquid-stable-donor-acceptor-interaction-solvent-free-liquid-state01093nas a2200205 4500008004100000022001400041245010400055210006900159260000800228300001400236490000700250520037300257100001900630700002100649700001700670700002600687700002400713700001900737856013100756 2023 eng d a1359-734500aOn the competition between six-membered and five-membered NHC towards alane centered ring expansion0 acompetition between sixmembered and fivemembered NHC towards ala cJUL a8540-85430 v593 a

The combination of 6-SIDipp center dot AlH3 (1) and 5-IDipp resulted in the ring expansion of 6-NHC, while the five-membered NHC remained unchanged, which was subsequently explained by DFT studies. Besides, the substitution chemistry of 1 was also studied with TMSOTf and I-2, which gave rise to the substitution of a hydride by triflate or iodide ligands.

1 aBalayan, Kajal1 aSharma, Himanshu1 aVanka, Kumar1 aRavindranathan, Sapna1 aGonnade, Rajesh, G.1 aSen, Sakya, S. uhttp://library.ncl.res.in/content/competition-between-six-membered-and-five-membered-nhc-towards-alane-centered-ring-expansion