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At least 253 records · Page 14Linked to original sources
PubMed1997

Lipid and protein deposition of N-vinyl pyrrolidone-containing group II and group IV frequent replacement contact lenses.

PURPOSE: The purpose of this study was to investigate the degree of protein and lipid deposition that occurs on N-vinyl-2-pyrrolidone (NVP) containing group II (non-ionic, high water content) and NVP containing group IV (ionic, high water content) frequent replacement hydrogel contact lens materials. METHODS: Twenty subjects were fitted with Group II (Vasurfilcon A) and Group IV (Vifilcon A) contact lenses, which were replaced monthly. The lenses were worn as a contralateral pair for 3 consecutive monthly periods. At the end of each monthly period, the lenses were collected for analysis of protein and lipid deposits. Protein deposition (following extraction) was examined by transmission UV and lipoidal deposition was examined using fluorescence spectrophotofluorimetry. RESULTS: There was a significant difference in the lipid and protein deposition profiles between the two materials. The Group II lens deposited approximately 2x more lipid (38 versus 73 fluorescence units; P < 0.0001) and the Group IV lens deposited approximately 17x more protein (488 micrograms versus 28 micrograms; P < 0.0001). Whilst the mean results across months were not significantly different for either protein or lipid (P = NS), the results revealed significant inter- and intra-subject variation. CONCLUSIONS: Protein deposition was predominantly controlled by the ionic charge of the lens materials, whereas the lipid deposition was predominantly determined by the NVP content. This study demonstrates that inter-subject variation and material characteristics significantly influence the deposition profile of hydrogel contact lens materials.

Adolescent↗
PubMed1997

The biosynthetic incorporation of selenomethionine and telluromethionine into pyrrolidone carboxyl peptidase (PYRase) from S. aureus.

Heavy-atom derivatives of PYRase proteins prepared in the past have been unsuitable for x-ray diffraction analysis. Thus, we propose utilizing unnatural metalloid-containing amino acids as an alternative to heavy-atom derivatization. Selenomethionine-containing proteins analyzed by multiwavelength anomalous diffraction provides a facile means of addressing the phase problem, whose solution is necessary to determine protein structures by X-ray Crystallography [Hendrickson, et al., 1991 and references therein]. Telluromethionine-containing proteins offer the same investigational potential, and additionally allow further simplification of the data collection technique by requiring only traditional methods of phase analysis [Boles et al., 1995 and references therein]. We sought to introduce the required Se and Te atoms into Staphylococcus aureus Pyrrolidone Carboxyl Peptidase (PYRase) via selenomethionine (SeMet) and telluromethionine (TeMet). Complete incorporation of SeMet into S. aureus PYRase was succeeded with little change in enzymatic properties. Incomplete incorporation (75%) of TeMet was accomplished in preparing TeMet-PYRase, however, representing the highest incorporation to date of a tellurium-containing amino acid. Enzymatic properties remained unchanged when TeMet was incorporated. We report herein the biosynthetic substitution and expression, protein purification and comparative biochemistry of SeMet-PYRase and TeMet-PYRase.

Crystallization↗
PubMed1976

The effect of amino acid restricted diets on the clearance of 125I-labelled polyvinyl pyrrolidone in mice.

Impaired overall phagocytic function, as measured by clearance of radio-labelled polyvinyl pyrrolidone from the blood (KPVP), has been demonstrated in mice whose dietary intake of the essential amino acids phenylalanine and tryptophan was reduced to less than a quarter of that in a standard diet which supported optimal growth. This was associated with loss in weight of body, liver, spleen and thymus and an increase in the phagocytic index, alphaPVP.

Amino Acids↗
PubMed1998

Interaction of sodium dehydrocholate and sodium cholate with polyvinyl pyrrolidone in aqueous medium.

The results of interaction of the bile salts sodium dehydrocholate (NaDHC) and sodium cholate (NaC) with the water soluble polymer polyvinyl pyrrolidone (PVP) studied by the methods of conductance, surface tension, viscosity and calorimetry are reported. Both of the bile salts exhibited PVP influenced self-aggregation. While NaC showed expected surface tension behaviour, NaDHC exhibited anomalous behaviour. The minimum interfacial area per molecule of the bile salt, the maximum interfacial adsorption, the free energy of micellization and the free energy of interfacial adsorption are presented for NaC. This information was not obtained for NaDHC because of its anomalous surface tension behaviour. The bile-salt-adhered PVP exhibited polyelectrolyte behaviour at PVP concentrations < 0.25 g dl-1. The enthalpy of interaction of NaC with PVP had a maximum at 0.25 mole dm-3 (delta Hi = +180 cal/mole); NaDHC produced too little heat to be detected by the calorimeter.

Cholic Acid↗