Biological Properties and Functions

It appears that cyclopropanoid fatty acids occur mainly esterified in position 2 of the various glycerolipids (Christie, 1970 Hofmann, 1963), the position usually occupied by a polyunsaturated acyl moiety. Phospholipids, in which either a cyclopropanoid fatty acid or a polyunsaturated fatty acid is esterified in position 2, exhibit similar physical properties (Christie, 1970 Hofmann, 1963). Although a systematic study of the distribution of the cy-clopropenoid fatty acids in the various positions of glycerolipids is yet to be carried out, it seems that these unusual fatty acids in seed oils are also predominantly esterified in position 2 (Christie, 1970). 

It was considered possible that cyclopentenyl fatty acids might be formed by oxidative ring closure of polyunsaturated straight-chain fatty acids 

The biosynthesis of lysine in higher plants involves the formation of a, e-diaminopimelate from aspartate and pyruvate. Transamination of this intermediate to the diketo compound and reduction of one carboxyl group to an aldehyde function may produce a compound capable of cyclization via aldol condensation, i.e., the C4 -I- C3 pathway.  

Incubations of cell suspension cultures of Idesia polycarpa and of seed tissue ofH. anthelminthic a with [l,2- C]a-ketopimelate proved the validity of the Cl chain elongation mechanism. Although in the systems tested this substrate was metabolized to some extent, cyclopentenylglycine was synthesized at a much higher rate from a-ketopimelate than from acetate. In a control experiment, cell suspension cultures of soya were incubated with [l,2- C]a-ketopimelate or [l- C]acetate, but cyclopentenylglycine was not synthesized in either case (Tober and Spener, 1980). 

The pivotal role of aleprolic acid (cyclopentenylcarboxylic acid) as primer in the biosynthesis of cyclopentenyl fatty acids was examined in a variety of tissues. In seeds of anthelminthica and C. echinata [l- C]aleprolic acid was almost exclusively incorporated into cyclopentenyl fatty acids, and in cells of I. polycarpa suspension cultures at a level of well over 60% (Cramer and Spener, 1976 Buchholz and Spener, 1980). In the cell cultures used, where endogenous cyclopentenyl fatty acids occurred only at a minor level, the substrate was taken up and activated for both anabolic and catabolic reactions. The acetate thus formed was refunneled and used for the de novo synthesis predominantly of straight-chain fatty acids (Buchholz and Spener, 1980). 

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Denny, M.W., Silks—their properties and function, in The Mechanical Properties of Biological Materials, Vincent, J.F.V. and Currey, J.D. (Eds.), Symposia of the Society for Experimental Biology no. 34, Cambridge University Press, Cambridge 1980, 247-272. 

The protein Ras, an important intracellular signal transducer, is crucially involved in the development of tumor growth. The farnesylation of Ras, catalyzed by the enzyme Ras-farnesyl-transferase, is essential to its proper functioning in the normal and in the transformed state. Therefore, the inhibition of Ras lipidation has become a promising target for the development of new classes of anti-tumor agents. This review focuses on the different classes of Ras-farnesyl-transferase inhibitors and compares their biological properties and modes of action in vitro as well as in vivo. 

Advanced characterization of the structure, properties and function of the self-assembled precursor can be extrapolated from studies on the more robust crosslinked material, especially in changing or challenging environments, in which the assemblies would not remain intact. The introduction of crosslinks has aided in the maintenance of native conformations as a powerful technique during studies to determine the order and structure of biological assemblies [61, 62], Moreover, the robust characteristics that the crosslinks provide, combined with the ability to define their regioselectivity, are expected to expand the realm of possible applications for nanoscale materials. 

A naturally occurring phenazine of nonbacterial origin is the methano-phenazine (MP) (10) which has been isolated from the cytoplasmic membrane of Methanosarcina (Ms.) mazei Gol archaea. The structure, synthesis, properties, and function of this natural product will be discussed in detail since it is not only the first and so far the sole phenazine derivative from archaea, but also the first one that is acting as an electron carrier in a respiratory chain - a biologic function equivalent to that of ubiquinones in mitochondria and bacteria. 

Membrane proteins (which make up approximately one-third of the total number of known proteins) are responsible for many of the important properties and functions of biological systems. They transport ions and molecules across the membrane they act as receptors and they have roles in the assembly, fusion, and structure of cells and viruses. Presently, investigating membrane proteins is one of the most difficult challenges in the area of structural biology and biophysical chemistry. Our knowledge of membrane proteins is limited, primarily because it is very difficult to crystallize these protein systems due to the extreme hydrophobic interactions between the proteins and the membrane. New methods are needed and current techniques need to be extended to study the structural properties of membrane proteins. 

This widespread recognition of the membranous nature of cellular organization suggests that a detailed physical and chemical characterization is of some importance to our understanding of biological processes. However, owing to the complexity of natural membranes, many investigators interested in cellular properties and function were compelled to... 

Typically, proteins fold to organize a very specific globular conformation, known as the protein s native state, which is in general reasonably stable and unique. It is this well-defined three-dimensional conformation of a polypeptide chain that determines the macroscopic properties and function of a protein. The folding mechanism and biological functionality are directly related to the polypeptide sequence a completely random amino acid sequence is unlikely to form a functional structure. In this view, polypeptide sequence... 

It is well documented that dietary proteins possess nutritional, functional and biological properties, and that these are often affected by the technological processes used in food manufacture and processing (Korhonen et al, 1998a). Proteins may also be added as functional ingredients to foods to emulsify, to bind water or fat, to form foams or gels, and to alter the flavor, appearance and texture (Anantharaman and Finot, 1993). The role of proteins as physiologically active components in the diet has been... 

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