Chemical Properties Of Lipids Research Articles

Multistage Delivery Technologies: Multifunctional, Interdisciplinary Approaches to Nanomedicine

Nanomedicine frequently employs single particles ranging from very simple1 to highly multifunctional.2 However, the diversity of barriers to effective transport can limit the global optimization of delivery for such systems. Multistage particles present an effective means to overcome such issues, allowing scientists to better segment the delivery mechanism into discrete steps by combining multiple formulations for sequential utility in vivo. A recent article in Nature Biotechnology highlights such a system,3 delivering nanoformulated doxorubicin (Dox) within larger disc-shaped, mesoporous silica particles (MSPs).

Membrane Protein Structure Determination in Membrana

The two principal components of biological membranes, the lipid bilayer and the proteins integrated within it, have coevolved for specific functions that mediate the interactions of cells with their environment. Molecular structures can provide very significant insights about protein function. In the case of membrane proteins, the physical and chemical properties of lipids and proteins are highly interdependent; therefore structure determination should include the membrane environment. Considering the membrane alongside the protein eliminates the possibility that crystal contacts or detergent molecules could distort protein structure, dynamics, and function and enables ligand binding studies to be performed in a natural setting. Solid-state NMR spectroscopy is compatible with three-dimensional structure determination of membrane proteins in phospholipid bilayer membranes under physiological conditions and has played an important role in elucidating the physical and chemical properties of biological membranes, providing key information about the structure and dynamics of the phospholipid components. Recently, developments in the recombinant expression of membrane proteins, sample preparation, pulse sequences for high-resolution spectroscopy, radio frequency probes, high-field magnets, and computational methods have enabled a number of membrane protein structures to be determined in lipid bilayer membranes. In this Account, we illustrate solid-state NMR methods with examples from two bacterial outer membrane proteins (OmpX and Ail) that form integral membrane β-barrels. The ability to measure orientation-dependent frequencies in the solid-state NMR spectra of membrane-embedded proteins provides the foundation for a powerful approach to structure determination based primarily on orientation restraints. Orientation restraints are particularly useful for NMR structural studies of membrane proteins because they provide information about both three-dimensional structure and the orientation of the protein within the membrane. When combined with dihedral angle restraints derived from analysis of isotropic chemical shifts, molecular fragment replacement, and de novo structure prediction, orientation restraints can yield high-quality three-dimensional structures with few or no distance restraints. Using complementary solid-state NMR methods based on oriented sample (OS) and magic angle spinning (MAS) approaches, one can resolve and assign multiple peaks through the use of (15)N/(13)C labeled samples and measure precise restraints to determine structures.

Computational models for the formation of protocell structures.

There have been various attempts to simulate the self-assembly process of lipid aggregates by computers. However, due to the computationally complex nature of the problem, previous simulations were often conducted with unrealistic simplifications of the molecules' morphology, intermolecular interactions, and the environment in which the lipid molecules interact. In this article, we present a new computational model in which each lipid is simulated by a more realistic amphiphilic particle consisting of a hydrophilic head and a long hydrophobic tail. The intermolecular interactions are approximated by a set of simple forces reflecting physical and chemical properties of lipids, for example, hydrophobicity and electrostatic forces, which are believed to be crucial for the formation of various aggregates. With a set of carefully selected parameters, this model is able to simulate successfully the formation of micelles in an aqueous environment and reversed micelle structures in an oil solvent from an initially randomly distributed set of lipidlike particles. This model can be used to study, at the microscopic level, the self-assembly of different protocell structures in the evolutionary process and the impact of environmental conditions on the formation of these structures. It may be further generalized to simulate the formation of other, more complex structures of amphiphilic molecules such as monolayer and bilayer aggregates.

ALTERATIONS OF MUSCLE PROTEIN FUNCTIONALITY BY OXIDATIVE AND ANTIOXIDATIVE PROCESSES1

ABSTRACTOxidation and resulting changes in physical and chemical properties of lipids and proteins occur widely in muscle foods, but oxidatively induced alterations in protein functionality have not been fully assessed. Recent studies have shown that sarcoplasmic, myofibrillar and stromal proteins, whether from red meat, poultry, or fish species, are all susceptible to oxidative damage caused by oxidizing lipids, metal ions, and other prooxidants indigenous to muscle or generated during meat processing. This is demonstrated by changes in protein structure, peptide chain scission, formation of amino acid derivatives and polymers, and decreases in solubility, gelation and hydration properties. However, utilization of antioxidants can minimize functional deteriorations in proteins during processing and storage, thereby assuring the supply of high‐quality muscle food products.

ADIPOSE TISSUE. MORPHOLOGICAL CHANGES ASSOCIATED WITH LIPID MOBILIZATION.

Morphological changes associated with mobilization of lipid were studied in epididymal adipose tissue from fasted and from alloxan diabetic rats. In both groups of animals a decrease in lipid content was accompanied by the formation of complex frond-like cytoplasmic processes and of loops and folds of basement membrane which extended from cell surfaces. These changes, evident after 1 day of fasting, increased in magnitude with increasing weight loss. As the lipid content of the cell decreased further, lipid-cytoplasmic interfaces became irregular and convoluted. Cytoplasmic microvesicles were prominent and appeared to be greatly increased in number. Rosette-like structures composed of microvesicles were observed in both lipid-depleted fat cells and endothelium. The interpretation of these changes and their physiological significance are discussed in terms of the physical and chemical properties of lipids and lipid metabolism. It is postulated that microvesicles may represent the mechanism of transport of free fatty acids in fat cells and in endothelium. Hypotheses are proposed and illustrated schematically for the mode of formation of microvesicular rosettes, for the mobilization and uptake of lipids by fat cells, and for the transport of lipids through endothelium.