Search results for "conformation"

5,11,17,23-Tetranitro-25,26,27,28-tetrapentyloxycalix[4]arene

2005

The mol­ecule of the title compound, C48H60N4O12, is located on a crystallographic twofold rotation axis. It is found in the typical pinched cone conformation. The dihedral angles between the reference plane (defined by the C atoms of the methyl­ene bridges) and the benzene rings are 83.33 (6) and 141.61 (5)°.

Dynamics of hyaluronan aqueous solutions as assessed by fast field cycling NMR relaxometry.

2010

Fast field cycling (FFC) NMR relaxometry has been used to study the conformational properties of aqueous solutions of hyaluronan (HYA) at three concentrations in the range 10 to 25 mg mL(-1). Results revealed that, irrespective of the solution concentration, three different hydration layers surround hyaluronan. The inner layer consists of water molecules strongly retained in the proximity of the HYA surface. Because of their strong interactions with HYA, water molecules in this inner hydration layer are subject to very slow dynamics and have the largest correlation times. The other two hydration layers are made of water molecules which are located progressively further from the HYA surface.…

Conformational Isomerism in Drug Action: Does the Free Energy of Binding Induce the Pharmacophoric Conformation of Semi-Rigid Muscarinic Agonists?

1974

The physiological neurotransmitter Acetylcholine has been shown to have great molecular flexibility, and because of this, the possibility of forming numerous energetically different conformations. This property makes the determination of the biologically active conformation extremely complicated. In attempts to solve this problem various research groups have tried two basically different approaches: (1) (1) The determination of the energetically most stable conformation using crystallographic methods (X-ray diffraction studies), nuclear magnetic resonance and quantum-mechanical calculations [1–16]. Same workers hypothesized that the energetically most favourable form was also the biological…

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

2014

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards understanding its mechanism. Protonation and conformational changes affect the vibration pattern of amino acid side chains and of the peptide bond, respectively, both of which can be probed by infrared (IR) difference spectroscopy. For proteins whose function can be repetitively and reproducibly triggered by light, it is possible to obtain infrared difference spectra with (sub)microsecond resolution over a broad spectral range using the step-scan Fourier transform infrared technique. With -10(2)-10(3) repetitions of the photoreaction, the minimum num…

RNAs That Behave Like Prions

2020

The term “prion” was originally coined to describe the proteinaceous infectious agents involved in mammalian neurological disorders. More recently, a prion has been defined as a nonchromosomal, protein-based genetic element that is capable of converting the copies of its own benign variant into the prion form, with the new phenotypic effects that can be transmitted through the cytoplasm. Some prions are toxic to the cell, are able to aggregate and/or form amyloid structures, and may be infectious in the wild, but none of those traits are seen as an integral property of all prions. We propose that the definition of prion should be expanded, to include the inducible transmissible entities und…

Crystallization and Preliminary X-Ray Analysis of Rotavirus Protein VP6

1998

ABSTRACT As a first step to gain insight into the structure of the rotavirus virion at atomic resolution, we report here the expression, purification, and crystallization of recombinant rotavirus protein VP6. This protein has the property of polymerizing in the form of tubular structures in solution which have hindered crystallization thus far. Using a combination of electron microscopy and small-angle X-ray scattering, we found that addition of Ca 2+ at concentrations higher than 100 mM results in depolymerization of the tubes, leading to an essentially monodisperse solution of trimeric VP6 even at high protein concentrations (higher than 10 mg/ml), thereby enabling us to search for crysta…

Photoinduced Electron Transfer in Multiporphyrinic Interlocked Structures: The Effect of Copper(I) Coordination in the Central Site

2004

Photoinduced processes have been determined in a [2]catenane containing a zinc(II) porphyrin, a gold(III) porphyrin, and two free phenanthroline binding sites, Zn-Au(+), and in the corresponding copper(I) phenanthroline complex, Zn-Cu(+)-Au(+). In acetonitrile solution Zn-Au(+) is present in two different conformations: an extended one, L, which accounts for 40 % of the total, and a compact one, S. In the L conformation, the electron transfer from the excited state of the Zn porphyrin to the gold-porphyrin unit (k = 1.3x10(9) s(-1)) is followed by a slow recombination (k = 8.3x10(7) s(-1)) to the ground state. The processes in the S conformation cannot be clearly resolved but a charge-separ…

Direct Identification of Each Specific Mutation in Codon 12 and 13 of ci-ki-ras2 by SSCP Analysis

1998

We compared the SSCP behaviour of the DNA fragments containing c-ki-ras 2 wild type 12 and 13 codons or each of the 12 possible point mutated sequences in these two codons. We found that a single electrophoresis condition was sufficient to distinguish each specific mutation from the other 11 and from the wild type sequence. This observation makes it possible to identify each specific mutation directly by SSCP without any need for reamplification and sequencing.

MOLECULAR DYNAMICS - MULTIPLE RECEPTOR CONFORMATIONS APPROACH TO ENHANCE STRUCTURE-BASED VIRTUAL SCREENING ON PPAR-alpha RECEPTOR

2016

Role of glycine-82 as a pivot point during the transition from the inactive to the active form of the yeast Ras2 protein

1991

AbstractRas proteins bind either GDP or GTP with high affinity. However, only the GTP-bound form of the yeast Ras2 protein is able to stimulate adenylyl cyclase. To identify amino acid residues that play a role in the conversion from the GDP-bound to the GTP-bound state of Ras proteins, we have searched for single amino acid substitutions that selectively affected the binding of one of the two nucleotides. We have found that the replacement of glycine-82 of the Ras2 protein by serine resulted in an increased rate of dissociation of Gpp(NH)p, a nonhydrolysable analog of GTP, while the GDP dissociation rate was not significantly modified. Glycine-82 resides in a region that is highly conserve…