Search results for "Nuclear magnetic resonance spectroscopy"
showing 10 items of 843 documents
Rapid one-pot synthesis of tapered star copolymers via ultra-fast coupling of polystyryllithium chain ends
2019
Highly efficient stoichiometric coupling of sterically hindered polystyryllithium (PS-Li) chain ends was achieved using tetra[3-(chloro-dimethylsilyl)propyl]silane (TCDMSPS) as the linking agent. Based on the disparate reactivities of isoprene (I, rI = 11.0) and styrene (S, rS = 0.049) in the anionic copolymerization in nonpolar media, poly(isoprene0.5-grad-styrene0.5) (P(I0.5-grad-S0.5)) tapered 4-arm star copolymers were synthesized in only two steps. The tapered 4-arm star copolymers (Mtargetedw = 40 to 160 kg mol−1) were synthesized with high star functionalities f (Mw,star/Mw,arm = 3.68–3.98), low dispersity (Đ = 1.06–1.15) and minimal residual precursor content (2–8 wt%), avoiding fra…
First bisphosphonate hydrogelators: potential composers of biocompatible gels
2020
Recently, investigation of hydrogels has gained ever increasing attention mostly because of their biomedical and pharmaceutical properties, and novel hydrogelators are constantly studied to find functional applications. Bisphosphonates (BPs) are well-known compounds applicable in different fields but are mostly used in clinics as drugs for bone-related diseases. In this study, a novel class of BP-hydrogelators together with a BP-organogelator was found, and the gelating abilities of the compounds were studied. Several techniques to analyze the structure and the properties of the formed gels were used, including solid state 13C and 31P CPMAS and solution state NMR spectroscopy, IR spectrosco…
Conformational Changes and Charge Transfer in Biomolecules Resolved Using Dynamic Enhanced Raman Correlation Spectroscopy
2019
International audience; In this contribution, we report that conforma-tional changes of molecules that are often buried in a wide-distributed Gaussian distribution can be discerned by analyzing the dynamics of specific Raman lines. We investigate the pertinence of the auto-and cross-correlation functions applied to the dynamics of three Raman lines of an amino acid, the tryptophan. The cross-correlation between intensity and the Raman band is an indicator of the charge transfer during the diffusion limited reaction of tryptophan and the gold surface. The Pećlet number Pe can provide a valuable indicator of the convective and/or diffusive features of each Raman band. Adsorption induced confo…
Simulated annealing with restrained molecular dynamics using CONGEN: Energy refinement of the NMR solution structures of epidermal and type-αtransfor…
1996
The new functionality of the program CONGEN (Bruccoleri RE, Karplus M, 1987, Biopolymers 26:137-168; Bassolino-Klimas D et al., 1996, Protein Sci 5:593-603) has been applied for energy refinement of two previously determined solution NMR structures, murine epidermal growth factor (mEGF) and human type-alpha transforming growth factor (hTGF alpha). A summary of considerations used in converting experimental NMR data into distance constraints for CONGEN is presented. A general protocol for simulated annealing with restrained molecular dynamics is applied to generate NMR solution structures using CONGEN together with real experimental NMR data. A total of 730 NMR-derived constraints for mEGF a…
Chemical constituents from leaves and root bark of Trichilia monadelpha (Meliaceae)
2018
Abstract Two new limonoid derivatives designated, monadelphin A (1) and monadelphin B (2) and two new sesquiterpene derivatives named trichins A (3) and B (4) were isolated together with six known compounds (5–10) from the mixture of methylene chloride/methanol (1:1) extract of leaves and root bark of Trichilia monadelpha (Meliaceae) collected in Cameroon. The structures of the new compounds were unambiguously established by detailed spectroscopic analysis including 1D and 2D NMR data in conjunction with high resolution mass spectrometry data and by comparison of these data with those of related compounds described in the literature. Compounds 1–4 were screened for their cytotoxic potential…
Halogenation of tellurium by SO2Cl2. Formation and crystal structures of (H3O)[Te3Cl13]·1/2SO2, [(C4H8O)2H][TeCl5]·(C4H8O), [(Me2SO)2H]2[TeCl6], and …
2002
Abstract The halogenation of elemental tellurium with SO2Cl2 in various solvents has been investigated. (H3O)[Te3Cl13]·1/2SO2 (1) and [(C4H8O)2H][TeCl5]·(C4H8O) (2) were obtained in CS2 and THF, respectively. When DMSO is added into the THF solution of tellurium and SO2Cl2, [(Me2SO)2H]2[TeCl6] (3) is formed. In the acetonitrile solution tellurium and SO2Cl2 form [Ni(NCCH3)6][Te2Cl10] (4) in the presence of metallic nickel. All compounds 1–4 were characterized by 125Te NMR and by X-ray crystallography. The formation of the anions has been discussed.
Hederagenin glycosides from the fruits of Blighia unijugata
2019
Abstract A phytochemical investigation of Blighia unijugata led to the isolation of eleven hederagenin glycosides. Among these compounds, six are previously undescribed, two are described in their native forms for the first time and three are known whereas firstly isolated from Blighia unijugata. The structure of the undescribed compounds was elucidated on the basis of 2D NMR and mass spectrometry analyses as 3-O-β-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosylhederagenin, 3-O-β-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 4)-3-O-acetyl-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyr…
A Model of Smart G-Quadruplex Ligand
2012
An unprecedented strategy to control the quadruplex- vs duplex-DNA selectivity of a ligand is reported. We designed a compound whose structure can rearrange when it interacts with a G-quadruplex, thereby controlling its affinity. Thus, the first "smart G-quadruplex ligand" is reported, since this ligand experiences a structural change in the presence of quadruplexes but not in the presence of duplexes, ensuring a high level of quadruplex selectivity.
Correction to ‘Secondary structure determination of conserved SARS-CoV-2 RNA elements by NMR spectroscopy’
2021
The current pandemic situation caused by the Betacoronavirus SARS-CoV-2 (SCoV2) highlights the need for coordinated research to combat COVID-19. A particularly important aspect is the development of medication. In addition to viral proteins, structured RNA elements represent a potent alternative as drug targets. The search for drugs that target RNA requires their high-resolution structural characterization. Using nuclear magnetic resonance (NMR) spectroscopy, a worldwide consortium of NMR researchers aims to characterize potential RNA drug targets of SCoV2. Here, we report the characterization of 15 conserved RNA elements located at the 5' end, the ribosomal frameshift segment and the 3'-un…
Thecis-transisomerization ofN-methyl-α,β-dehydroamino acids
2012
Dehydroamino acids with the methylated N-terminal peptide group occur in natural small cyclic peptides. The structural analysis was used to investigate the cis-trans isomerization of the N-terminal tertiary amide group of diamides: Ac-(Z)-Δ(Me)Abu-NHMe (1), Ac-(Z)-Δ(Me)Phe-NHMe (2), Ac-(E)-Δ(Me)Phe-NHMe (3), Ac-Δ(Me)Ala-NHMe (4), and Ac-(Me)Ala-NHMe (5). The compounds were analyzed in the solid state by an X-ray crystallography (1-3), and in the solution by FTIR (MeCN and CHCl(3) ) and NMR (DMSO-d6 and CDCl(3) ) methods (1-5). In the solid state, the studied compounds adopt the cis configuration of N-terminal amide. In solution, this configuration also prevails for the dehydroamino acids 1-…