The encapsulation of enzymes and other proteins into inorganic host materials has attracted considerable attention over the past few years This research has demonstrated that biomolecules immobilized in inorganic matrixes retain their functional characteristics to a large extent These new materials are of interest for applications as (optically based) biosensors and biocatalysts We review the growing field of amino acids, vitamins, enzymes, and whole cells adsorbed (immobilized) onto ordered mesoporous silica and carbon molecular sieves Strategies for the preparation of mesoporous supports and the essential properties of the resulting materials with respect to the envisaged applications are presented Basic effects of the nature of the adsorption and various aspects of the application of these materials as biosensors, bicatalysts, and for drug release are discussed Outlook of potential applications and further challenges are also provided

Ordered Mesoporous Materials for Bioadsorption and Biocatalysis

Structure of the inverted hexagonal (HII) phase, and non-lamellar phase transitions of lipids.

Phospholipids play multiple roles in cells by establishing the permeability barrier for cells and cell organelles, by providing the matrix for the assembly and function of a wide variety of catalytic processes, by acting as donors in the synthesis of macromolecules, and by actively influencing the functional properties of membrane-associated processes. The function, at the molecular level, of phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin in specific cellular processes is reviewed, with a focus on the results of combined molecular genetic and biochemical studies in Escherichia coli. These results are compared with primarily biochemical data supporting similar functions for these phospholipids in eukaryotic organisms. The wide range of processes in which specific involvement of phospholipids has been documented explains the need for diversity in phospholipid structure and why there are so many membrane lipids.

MOLECULAR BASIS FOR MEMBRANE PHOSPHOLIPID DIVERSITY: Why Are There So Many Lipids?

The role of alterations in membrane lipid composition in enabling physiological adaptation of organisms to their physical environment.

Lipid–protein interactions in biological membranes: a structural perspective

Microbial biohydrogenation of oleic acid to trans isomers in vitro

Seashore paspalum (Paspalum vaginatum Sw.) is a warm-season turfgrass, best known for its superior salt tolerance. Plants are subject to injury during winter conditions along the northern boundary of their zone of adaptation. New cultivars that are more tolerant to low temperatures are needed for use in the transition zone. Cold tolerance has been correlated with the degree of unsaturation in membrane lipid fatty acids. Unsaturated fatty acids are thought to aid in maintaining membranes in a fluid state necessary for biological functioning (homeophasic adaptation). The primary objective was to characterize fatty add composition of membrane lipids in three genotypes differing in cold tolerance. A second objective was to investigate changes in fatty acid content in these genotypes during exposure to low temperatures. Cold-treated plants were exposed to a 10-h photoperiod at 8°/4°C day/night temperatures and light intensity of 250 μmol m -2 s -1 photosynthetic photon flux density for 3 wk. Rhizomes and crowns were harvested at 7-d intervals. Total lipids were extracted and the polar lipids separated by thin-layer chromatography. Fatty acids were identified by gas chromatography (GC) and mass spectroscopy. In all three genotypes, the two saturated fatty acids, palmitic acid and stearic acid, did not change during cold treatment. The triunsaturated linolenic acid increased significantly during low temperature exposure. The magnitude of change was greater in the finer-textured and more cold-tolerant PI 509018-1 ('Sealslel') than in the intermediately cold-tolerant 'Adalayd' or in the cold-susceptible, coarse-textured PI 299042. These findings suggest that accumulation of linolenic add partly explains the differential response in their cold tolerance.

Changes in Membrane Polar Lipid Fatty Acids of Seashore Paspalum in Response to Low Temperature Exposure

Activation of beef-heart cytochrome c oxidase by cardiolipin and analogues of cardiolipin

The polymorphic phase behavior of cardiolipin (diphosphatidylglycerol) analogues with two to five chains per phospholipid head group, namely, dilysocardiolipin, monolysocardiolipin, cardiolipin, and acylcardiolipin, respectively, has been studied by 31P NMR and X-ray diffraction. Dilysocardiolipin dispersions at low salt concentration are micellar, and a transition to a lamellar phase takes place between 1 and 2 M NaCl. From light-scattering measurements, it is also found that a transition takes place from the micellar state with a midpoint at 5.2 mM CaCl2, 0.95 M HClO4, and 1.5 M NaCl. Monolysocardiolipin dispersions are lamellar throughout the concentration range from zero to saturated NaCl. Cardiolipin dispersions undergo a transition from a lamellar to an inverted hexagonal phase between 1 and 2 M NaCl. Acylcardiolipin dispersions are in an inverted hexagonal phase throughout the concentration range from zero to saturated NaCl. The chemical shift anisotropies of both phosphate groups in dilysocardiolipin and of one of the phosphate groups in monolysocardiolipin are drastically reduced in the lamellar phase, indicating a different conformation of the phosphatidyl head group from that normally found in diacyl phospholipid bilayers. The results provide strong support for the "shape" concept of lipid polymorphism when viewed in its most general form including configurational entropy, hydrophobic effects, etc. and indicate the importance of head-group interactions in determining the lipid phase behavior.

Polymorphic phase behavior of cardiolipin derivatives studied by 31P NMR and X-ray diffraction.

The fully oxidized complex of cytochrome c and cytochrome oxidase formed at low ionic strength was studied by resonance Raman spectroscopy. The spectra of the complex and of the individual components were compared over a wide frequency range using Soret band excitation. In both partners of the complex, structural changes occur in the heme groups and in their immediate protein environment. The spectra of the complex in the 1600-1700 cm-1 frequency range were dominated by bands from the cytochrome oxidase component, whereas those in the 300-500 cm-1 range were dominated by bands from the cytochrome c component, hence allowing separation of the contributions from the two individual species. For cytochrome c, spectral changes were observed which correspond to the induction of the conformational state I and the six-coordinated low-spin configuration of state II on binding to cytochrome oxidase. While in state I the structure of cytochrome c is essentially the same as in solution, state II is characterized by a structural rearrangement of the heme pocket, leading to a weakening of the axial iron-methionine bond and an opening of the heme crevice which is situated in the center of the binding domain for cytochrome oxidase. The relative contributions of the two cytochrome c states were estimated to be approximately in the ratio 1:1 in the complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Gary L. Powell

Papers

Microbial biohydrogenation of oleic acid to trans isomers in vitro

Changes in Membrane Polar Lipid Fatty Acids of Seashore Paspalum in Response to Low Temperature Exposure

Activation of beef-heart cytochrome c oxidase by cardiolipin and analogues of cardiolipin

Polymorphic phase behavior of cardiolipin derivatives studied by 31P NMR and X-ray diffraction.

Conformational changes in cytochrome c and cytochrome oxidase upon complex formation: A resonance Raman study.