Search results for "protein crystallization"

On the application of an experimental multipolar pseudo-atom library for accurate refinement of small-molecule and protein crystal structures

2007

International audience; With an increasing number of biomacromolecular crystal structures being measured to ultra-high resolution, it has become possible to extend to large systems experimental charge-density methods that are usually applied to small molecules. A library has been built of average multipole populations describing the electron density of chemical groups in all 20 amino acids found in proteins. The library uses the Hansen & Coppens multipolar pseudo-atom model to derive molecular electron density and electrostatic potential distributions. The library values are obtained from several small peptide or amino acid crystal structures refined against ultra-high-resolution X-ray diff…

3D Electron Diffraction: The Nanocrystallography Revolution

2019

Crystallography of nanocrystalline materials has witnessed a true revolution in the past 10 years, thanks to the introduction of protocols for 3D acquisition and analysis of electron diffraction data. This method provides single-crystal data of structure solution and refinement quality, allowing the atomic structure determination of those materials that remained hitherto unknown because of their limited crystallinity. Several experimental protocols exist, which share the common idea of sampling a sequence of diffraction patterns while the crystal is tilted around a noncrystallographic axis, namely, the goniometer axis of the transmission electron microscope sample stage. This Outlook review…

Hemoglobin dynamics in rat erythrocytes investigated by M�ssbauer spectroscopy

1991

Rats have been enriched in 57Fe and erythrocytes were isolated from the blood. Mössbauer absorption spectroscopy on the hemoglobin of these erythrocytes has shown rather similar dynamics as found earlier in crystals of myoglobin, in frozen solutions of human hemoglobin and in a number of other proteins. The results strongly indicate that the motion of the heme and presumably some part of the F-helix is mainly influenced by the average viscosity of the sample determined by a network of hydrogen bridges and other weak interactions. Extrapolations of Mössbauer results from protein crystals to proteins in their physiological surroundings seem to be suitable for heme proteins.

Infrared Microspectroscopy study of insulin crystals at high pressure

2012

During the last years the coupling of high pressure techniques and infrared spectroscopy has proven to be a very powerful tool in the study of conformational changes of proteins. Protein unfolding and monomerization are events that are expected to take place at high pressure due to the peculiarity of pressure to shift the system towards the state that occupies the minimum volume. We observed the growth of apparently cubic crystals at a pressure of about 4 kbar, subjecting to high pressure a solution of misfolded insulin. Even if high pressure is commonly used to tune the growth rate of crystals, protein crystallization at high pressure is not a well known process and no evidences of the par…

2019

A probabilistic discrete model for 2D protein crystal growth is presented. This model takesinto account the available space and can describe growing processes of a different nature due to theversatility of its parameters, which gives the model great flexibility. The accuracy of the simulation istested against a real recrystallization experiment, carried out with the bacterial protein SbpA fromLysinibacillus sphaericus CCM2177, showing high agreement between the proposed model and theactual images of the crystal growth. Finally, it is also discussed how the regularity of the interface(i.e., the curve that separates the crystal from the substrate) affects the evolution of the simulation.

Protein crystallization: universal thermodynamic vs. specific effects of PEG

2008

The interest of nucleation of protein crystals and aggregates (including oligomerization) spans from basic physics theory all the way to biophysics, nanophysics, clinical sciences, biotechnologies, food technologies and polymer–solvent interactions. Understanding nucleation within a theoretical framework capable of providing quantitative predictions and control of nucleation rates, or even the very occurrence of crystallization, is a long-sought goal of remarkable relevance to each of the above fields. A large amount of work has been aimed at such goal, but success has been so far rather limited. Work at our laboratory has more recently highlighted a direct link between nucleation rates and…

Time scale of protein aggregation dictated by liquid-liquid demixing

2003

The growing impact of protein aggregation pathologies, together with the current high need for extensive information on protein structures are focusing much interest on the physics underlying the nucleation and growth of protein aggregates and crystals. Sickle Cell Hemoglobin (HbS), a point-mutant form of normal human Hemoglobin (HbA), is the first recognized and best-studied case of pathologically aggregating protein. Here we reanalyze kinetic data on nucleation of deoxy-HbS aggregates by referring them to the (concentration-dependent) temperature Ts characterizing the occurrence of the phase transition of liquid-liquid demixing (LLD) of the solution. In this way, and by appropriate scalin…

Inter- and intramolecular motions in proteins

1992

The use of 57 Fe Mossbauer radiation allows the study of protein crystal dynamics by a time-resolved analysis of X-ray scattering. In myoglobin crystals, the main source of the root mean squared amplitude of motions come from intramolecular protein dynamics. Segments of the size of an α-helix move collectively. Long-range correlated motions give only a minor contribution. Comparison with Mossbauer absorption spectroscopy shows that protein-specific dynamics is frozaen out below 200 K and the lattice dynamics in mainly responsible for the low-temperature behavior

Discussion on "Protein crystallization: universal thermodynamic vs. specific effects of PEG"

2008

Lysozyme crystallization rates controlled by anomalous fluctuations

2005

Abstract Nucleation of protein aggregates and crystals is a process activated by statistical fluctuations of concentration. Nucleation rates may change by several orders of magnitude upon apparently minor changes in the multidimensional space of parameters (temperature, pH, protein concentration, salt type and concentrations, additives). We use available data on hen egg lysozyme crystal induction times in different solution conditions. We measure by static and dynamic light scattering the amplitudes and lifetimes of anomalously ample and long-lived fluctuations occurring in proximity of the liquid–liquid demixing region of the given lysozyme solutions. This allows determining the related sp…