Freeze-thawing induced structural and functional changes in glucose oxidase.

Background: Glucose oxidase enzyme may be a suitable model for studying the effect of low temperatures on structural and functional properties of biomacromolecules.

Objective: The research aim was to study the freeze-thawing effect on glucose oxidase isolated and immobilized by cross-linking with glutaraldehyde

Methods: Effects of freezing rates on conformation and activity of glucose oxidase isolated and cross-linked in solution with gluteraldehyde was studied.

Results: Freezing with slow rate (2 degree C per min) induces significant protein aggregation, activity reduction and conformational changes in polar and hydrophobic regions.

Ocular anatomy, ganglion cell distribution and retinal resolution of a killer whale (Orcinus orca).

Retinal topography, cell density and sizes of ganglion cells in the killer whale (Orcinus orca) were analyzed in retinal whole mounts stained with cresyl violet. A distinctive feature of the killer whale's retina is the large size of ganglion cells and low cell density compared to terrestrial mammals. The ganglion cell diameter ranged from 8 to 100 µm, with the majority of cells within a range of 20-40 µm.

[Antioxidant properties of proteins after freezing-thawing].

Experimental data are presented which were obtained under comparative evaluation of influence of different freezing-thawing conditions on antioxidant properties of isolated proteins: human serum albumin, cytochrome c from the horse heart and glucose oxidase from Aspergillus niger. The observed protein antioxidant activity alterations are assumed to be a result of protein conformational changes. The character of freezing-thawing influence on the protein antioxidant activity depends on the molecular structure and cooling conditions.

[Effect of freezing on cord blood serum proteins].

The effect of freezing regimes and storage temperatures on protein conformation and the spectrum of cord blood serum has been investigated. Changes in the parameters of ESR spectra of spin probes in cord blood serum after slow freezing and subsequent thawing were established, indicating protein conformational changes characterized by loosening. This fact is confirmed by an earlier process, the first stage of albumin heat denaturation, as indicated by calorimetric data.