Search PubMed⌕ Search

Biomedical subjects

L J DeLucas

Publications and source records attributed to L J DeLucas.

42 records · Page 3Linked to original sources
PubMed1990

Purification of octyl beta-D-glucopyranoside and re-estimation of its micellar size.

The commercial non-ionic detergent octyl beta-D-glucopyranoside is often contaminated by significant amounts of UV absorbing and/or ionic compounds that can associate with membrane proteins. Such impurities can be monitored by several techniques (i.e., spectrophotometry, size exclusion chromatography, and pH, conductivity, and surface tension measurements) and can be removed using mixed-bed ion exchange chromatography. High performance size exclusion chromatography, dynamic light scattering, and ultracentrifugation have been used to re-estimate the size of micelles of octyl beta-D-glucopyranoside since previously published data varied over a wide range. Aggregation numbers were 27 to 100 for micellar molecular weights 8000 to 29,000. Direct physical methods that do not perturbate the sample indicated a large size for the micelles (hydrodynamic radius 23 +/- 3 A; Mr 22,000 +/- 3000; aggregation number 75 +/- 10 for a 34 mM aqueous solution). In contrast the chromatographic micellar size appeared to be smaller (hydrodynamic radius 15 +/- 1 A; Mr 8000 +/- 1000; aggregation number 27). This underestimation may be the result of adsorption and/or alteration of the micelles.

Chemical Phenomena↗
PubMed1990

Large scale preparation of homogeneous bacteriorhodopsin.

Homogeneous bacteriorhodopsin was obtained preparatively (100 mg batches) from purple membrane of Halobacterium halobium cells. The homogeneity of the protein was considerably affected by variations in the growth conditions of the bacteria. Fully matured bacteriorhodopsin having a blocked N-terminus and a homogeneous C-terminus, was reproducibly obtained when cells were grown in a sufficiently aerated medium.

Amino Acid Sequence↗
PubMed1989

Protein crystal growth in microgravity.

The crystals of most proteins or other biological macromolecules are poorly ordered and diffract to lower resolutions than those observed for most crystals of simple organic and inorganic compounds. Crystallization in the microgravity environment of space may improve crystal quality by eliminating convection effects near growing crystal surfaces. A series of 11 different protein crystal growth experiments was performed on U.S. space shuttle flight STS-26 in September 1988. The microgravity-grown crystals of gamma-interferon D1, porcine elastase, and isocitrate lyase are larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions than the best crystals of these proteins grown on Earth.

Animals↗
PubMed1987

Preliminary X-ray study of crystals of human C-reactive protein.

Two different crystal forms of human C-reactive protein have been grown from solutions of 2-methyl-2,4-pentanediol. Both crystal forms are tetragonal, the space group for form I is P4(1)22 (or P4(3)22), and that for form II is P4(2)22. The unit cell parameters for form I are a = b = 103.0(5) A, c = 308.5(7) A and for form II are a = b = 103.1(2) A, c = 312.7(6) A. The crystals of form II diffract to at least 3.0 A resolution, and are suitable for detailed structural studies.

C-Reactive Protein↗
PubMed1985

Isolation of detergent-solubilized monomers of bacteriorhodopsin by size-exclusion high-performance liquid chromatography.

Bacteriorhodopsin, an integral membrane protein of purple membranes, was solubilized with n-octylglucoside and isolated as intact monomeric micelles by high-performance size-exclusion chromatography. It was shown that separation was obtained between these micelles and either those containing bacterio-opsin or retinal as well as bacterio-opsin in the aggregated state. Estimates of the apparent molecular weights and Stokes radii were obtained by comparison with water-soluble proteins with known properties. Thermal denaturation of the native protein micelle induced the formation of a denatured species, which was similar to that found from denaturation at 4 degrees C.

Bacteriorhodopsins↗