Globular

S. A. Safran, Theory of Structure and Phase Transitions in Globular Microemulsions, in Micellar Solutions and Microemulsions, S. H. Chen and R. Rajagopalan, eds.. Springer-Verlag, New York, 1990, Chapter 9. 

Materials have many properties that are important, scientifically and teclmologically, that do not depend on the details of long-range stnicture. For example, consider a solution of globular macromolecules in a solvent... 

Figure C2.3.15. Hemimicelle stmctures (a) monolayer type hemimicelle (b) spheroidal, globular hemimicelle.

The behaviour of tliese systems is similar to tliat of suspensions in which short-range attractions are induced by changing solvent quality for sterically stabilized particles (e.g. [103]). Anotlier case in which narrow attractions arise is tliat of solutions of globular proteins. These crystallize only in a narrow range of concentrations [104]. 

Baker E N and Flubbard R E 1984 Hydrogen bonding in globular proteins Prog. Biophys. Molec. Biol. 44 97-179... 

Flaynes C A and Norde W 1994 Globular proteins at solld/llquid Interfaces Colloids Surf. B 2 517-66... 

Fig. 2. Correlation between predicted and experimental pKaS in 4 globular proteins...

Water-soluble globular proteins usually have an interior composed almost entirely of non polar, hydrophobic amino acids such as phenylalanine, tryptophan, valine and leucine witl polar and charged amino acids such as lysine and arginine located on the surface of thi molecule. This packing of hydrophobic residues is a consequence of the hydrophobic effeci which is the most important factor that contributes to protein stability. The molecula basis for the hydrophobic effect continues to be the subject of some debate but is general considered to be entropic in origin. Moreover, it is the entropy change of the solvent that i... 

Cohen F E, M J E Sternberg and W R Taylor 1982 Analysis and Prediction of the Paclung oi. i-E a iinst a /3-Sheet in the Tertiary Structure of Globular Proteins. Journal of AdoljcuLir E 156 821-862. 

Gamier J, D Osguthorpe and B Robson 1978. Analysis of the Accuracy and ImpUcatiotrs of Simple Mel for Predicting the Secondary Structure of Globular Proteins. Journal of Mokadar Biology 120 97-i... 

Nlng Q and T J Sejnowsld 1988. Predicting the Secondary Structure of Globular Proteins Using Neural Network Models. Journal of Molecular Biology 202 865-888. 

M J1990. Calculation of Conformational Ensembles from Potentials of Mean Force. An Approach o the Knowledge-Based Prediction of Local Structures in Globular Proteins. Journal of Molecular Siology 213 859-883. 

Separatory funnels. For many operations the globular form (compare Fig. II, 1, 5, c) with 14, 19 or 24 cone on the stem and 14 or 19 socket for the stopper, is convenient. For some purposes, e.g., when used on a three-necked flask or with a multiple adapter, the cylindrical... 

The electronic spatial extent is a single number that attempts to describe the size of a molecule. This number is computed as the expectation value of electron density times the distance from the center of mass of a molecule. Because the information is condensed down to a single number, it does not distinguish between long chains and more globular molecules. 

Many globular proteins are enzymes They accelerate the rates of chemical reactions m biological systems but the kinds of reactions that take place are the fundamental reactions of organic chemistry One way m which enzymes accelerate these reactions is by bringing reactive func tions together m the presence of catalytically active functions of the protein... 

Globular protein (Section 27 20) An approximately spheri cally shaped protein that forms a colloidal dispersion in water Most enzymes are globular proteins Glycogen (Section 25 15) A polysaccharide present in animals that IS denved from glucose Similar in structure to amy lopectin... 

Dill, KA. Theory for the folding and stability of globular proteins. Biochemistry 24 1501-1509, 1985. 

A model which is attracting increasing attention, because of its relevance to actual solids composed of globular particles (Section 1.6), is the packed sphere model. By applying the same general principles as those outlined... 

Hydrogen bonding stabilizes some protein molecules in helical forms, and disulfide cross-links stabilize some protein molecules in globular forms. We shall consider helical structures in Sec. 1.11 and shall learn more about ellipsoidal globular proteins in the chapters concerned with the solution properties of polymers, especially Chap. 9. Both secondary and tertiary levels of structure are also influenced by the distribution of polar and nonpolar amino acid molecules relative to the aqueous environment of the protein molecules. Nonpolar amino acids are designated in Table 1.3. 

Equation (8.97) shows that the second virial coefficient is a measure of the excluded volume of the solute according to the model we have considered. From the assumption that solute molecules come into surface contact in defining the excluded volume, it is apparent that this concept is easier to apply to, say, compact protein molecules in which hydrogen bonding and disulfide bridges maintain the tertiary structure (see Sec. 1.4) than to random coils. We shall return to the latter presently, but for now let us consider the application of Eq. (8.97) to a globular protein. This is the objective of the following example. 

Fig. 10. Selectivity curves A—D for Sephadex G-75, G-lOO, G-150, and G-200, respectively, for globular proteins.

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