11 research outputs found
Applied Crystallography The LaueUtil toolkit for Laue photocrystallography. I. Rapid orientation matrix determination for intermediate-size-unit-cell Laue data
A new method for determination of the orientation matrix of Laue X-ray data is presented. The method is based on matching of the experimental patterns of central reciprocal lattice rows projected on a unit sphere centered on the origin of the reciprocal lattice with the corresponding pattern of a monochromatic data set on the same material. This technique is applied to the complete data set and thus eliminates problems often encountered when single frames with a limited number of peaks are to be used for orientation matrix determination. Application of the method to a series of Laue data sets on organometallic crystals is described. The corresponding program is available under a Mozilla Public License-like open-source license
On the DMSO-Dissolved State of Insulin: A Vibrational Spectroscopic Study of Structural Disorder
Upon dissolving in dimethyl sulfoxide (DMSO), native
insulin and
insulin amyloid fibrils convert into an identical disordered structural
state based on IR spectral characteristics. Here, we investigate the
DMSO-denatured state of insulin using a number of spectroscopic methods:
near-UV circular dichroism, infrared absorption spectroscopy, vibrational
circular dichroism (VCD), Raman scattering, and Raman optical activity
(ROA), as well as by carrying out 140-ns-long molecular dynamics (MD)
simulations of DMSO-dissolved native insulin monomers. According to
this work, the DMSO-solvated state of insulin is an ensemble of conformations
including polyproline II-type helix and possibly a residual α-helical
structure. Effects of DMSO-specific solvation and conformation-restricting
covalent structure of insulin (including the three intact disulfide
bridges) are argued to play important roles in stabilizing the disordered
state of the protein. A comparison of ROA spectra of insulin dissolved
in fully deuterated and nondeuterated DMSO suggested transfer of chirality
from the protein to the otherwise ROA-silent solvent. Our study provides
an example of a biological protein that acquires a substantial population
of PP II conformation in an entirely nonaqueous environment. The DMSO-unfolded
state of insulin and its dynamics are also discussed in the context
of the established link between PP II conformation and protein misfolding
Recommended from our members
DiSCaMB: a software library for aspherical atom model X-ray scattering factor calculations with CPUs and GPUs.
It has been recently established that the accuracy of structural parameters from X-ray refinement of crystal structures can be improved by using a bank of aspherical pseudoatoms instead of the classical spherical model of atomic form factors. This comes, however, at the cost of increased complexity of the underlying calculations. In order to facilitate the adoption of this more advanced electron density model by the broader community of crystallographers, a new software implementation called DiSCaMB, 'densities in structural chemistry and molecular biology', has been developed. It addresses the challenge of providing for high performance on modern computing architectures. With parallelization options for both multi-core processors and graphics processing units (using CUDA), the library features calculation of X-ray scattering factors and their derivatives with respect to structural parameters, gives access to intermediate steps of the scattering factor calculations (thus allowing for experimentation with modifications of the underlying electron density model), and provides tools for basic structural crystallographic operations. Permissively (MIT) licensed, DiSCaMB is an open-source C++ library that can be embedded in both academic and commercial tools for X-ray structure refinement
Recommended from our members
DiSCaMB: a software library for aspherical atom model X-ray scattering factor calculations with CPUs and GPUs.
It has been recently established that the accuracy of structural parameters from X-ray refinement of crystal structures can be improved by using a bank of aspherical pseudoatoms instead of the classical spherical model of atomic form factors. This comes, however, at the cost of increased complexity of the underlying calculations. In order to facilitate the adoption of this more advanced electron density model by the broader community of crystallographers, a new software implementation called DiSCaMB, 'densities in structural chemistry and molecular biology', has been developed. It addresses the challenge of providing for high performance on modern computing architectures. With parallelization options for both multi-core processors and graphics processing units (using CUDA), the library features calculation of X-ray scattering factors and their derivatives with respect to structural parameters, gives access to intermediate steps of the scattering factor calculations (thus allowing for experimentation with modifications of the underlying electron density model), and provides tools for basic structural crystallographic operations. Permissively (MIT) licensed, DiSCaMB is an open-source C++ library that can be embedded in both academic and commercial tools for X-ray structure refinement
Restricted Photochemistry in the Molecular Solid State: Structural Changes on Photoexcitation of Cu(I) Phenanthroline Metal-to-Ligand Charge Transfer (MLCT) Complexes by Time-Resolved Diffraction
The excited-state structure of [Cu<sup>I</sup>[(1,10-phenanthroline-<i>N</i>,<i>N</i>′) bisÂ(triphenylphosphine)] cations
in their crystalline [BF<sub>4</sub>] salt has been determined at
both 180 and 90 K by single-pulse time-resolved synchrotron experiments
with the modified polychromatic Laue method. The two independent molecules
in the crystal show distortions on MLCT excitation that differ in
magnitude and direction, a difference attributed to a pronounced difference
in the molecular environment of the two complexes. As the excited
states differ, the decay of the emission is biexponential with two
strongly different lifetimes, the longer lifetime, assigned to the
more restricted molecule, becoming more prevalent as the temperature
increases. Standard deviations in the current Laue study are very
much lower than those achieved in a previous monochromatic study of
a CuÂ(I) 2,9-dimethylphenanthroline substituted complex (J. Am. Chem. Soc. 2009, 131, 6566), but the
magnitudes of the shifts on excitation are similar, indicating that
lattice restrictions dominate over the steric effect of the methyl
substitution. Above all, the study illustrates emphatically that molecules
in solids have physical properties different from those of isolated
molecules and that their properties depend on the specific molecular
environment. This conclusion is relevant for the understanding of
the properties of molecular solid-state devices, which are increasingly
used in current technology