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Results for “Cross-Linking Reagents/chemistry”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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3 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Organization of photosystem I polypeptides examined by chemical cross-linking

Photosystem I from the cyanobacterium Synechocystis sp. PCC 6803 was examined using the chemical cross-linkers glutaraldehyde and N-ethyl-1-3-[3-(dimethylamino)propyl]carbodiimide to investigate the organization of the polypeptide subunits. Thylakoid membranes and photosystem I, which was isolated by Triton X-100 fractionation, were treated with cross-linking reagents and were resolved using a Tricine/urea low-molecular-weight resolution gel system. Subunit-specific antibodies and western blotting analysis were used to identify the components of cross-linked species. These analyses identified glutaraldehyde-dependent cross-linking products composed of small amounts of PsaD and PsaC, PsaC and PsaE, and PsaE and PsaF. The novel cross-link between PsaE and PsaF was also observed following treatment with N-ethyl-1-3-[3-(dimethylamino)propyl]carbodiimide. These cross-linking results suggest a structural interaction between PsaE and PsaF and predict a transmembrane topology for PsaF.

NASA Discipline Plant Biology↗
NASA NTRS1994

In-situ polymerized PLOT columns III: divinylbenzene copolymers and dimethacrylate homopolymers

Studies of divinylbenzene copolymers and dimethacrylate homopolymers indicate that the polymer pore size controls the separation of water and ammonia on porous-layer-open-tubular (PLOT) columns. To a lesser degree, the polarity of the polymers also affects the separation of a water-ammonia gas mixture. Our results demonstrate that the pore size can be regulated by controlling the cross-linking density or the chain length between the cross-linking functional groups. An optimum pore size will provide the best separation of water and ammonia.

NASA Discipline Exobiology↗
NASA NTRS1997

Mineral induction by immobilized phosphoproteins

Dentin phosphoproteins are thought to have a primary role in the deposition of mineral on the collagen of dentin. In this study we determined the type of binding between collagen and phosphoproteins necessary for mineral formation onto collagen fibrils and whether the phosphate esters are required. Bovine dentin phosphophoryn or phosvitin from egg yolk were immobilized on reconstituted skin type I collagen fibrils by adsorption or by covalent cross-linking. In some samples the ester phosphate was removed from the covalently cross-linked phosphoproteins by treatment with acid phosphatase. All samples were incubated at 37 degrees C in metastable solutions that do not spontaneously precipitate. Reconstituted collagen fibrils alone did not induce mineral formation. The phosphoproteins adsorbed to the collagen fibrils desorbed when the mineralization medium was added, and mineral was not induced. The mineral induced by the cross-linked phosphoproteins was apatite, and the crystals were confined to the surface of the collagen fibrils. With decreasing medium saturation the time required for mineral induction increased. The interfacial tensions calculated for apatite formation by either phosphoprotein cross-linked to collagen were about the same as that for phosphatidic acid liposomes and hydroxyapatite. This similarity in values indicates that the nucleation potential of these highly phosphorylated surfaces is about the same. It is concluded that phosphoproteins must be irreversibly bound to collagen fibrils for the mineralization of the collagen network in solutions that do not spontaneously precipitate. The phosphate esters of phosphoproteins are required for mineral induction, and the carboxylate groups are not sufficient.

Non-NASA Center↗