Compact globule

Efimov, A.V. Stereochemistry of a-helices and (l-sheet packing in compact globule. /. Mol. Biol. 

Mel nikov, S.M., Sergeyev, V.G. and Yoshikawa, K. (1995b) Transition of double-stranded DNA chains between random coil and compact globule states induced by cooperative binding of cationic surfactants. J. Am. Chem. Soc., 117,9951-9956. 

The formation of a compact globule in copolymers requires them to have specific conformations, which are reached through local conformational fluctuations. A characteristic collapse time may be defined as for instance the time for which the gyration radius reaches its equilibrium value. This time measures the approach to equilibrium for the system and is related to the mean first passage time. 

For a relatively small linear poly (ethylene) chain of molecular weight 10,000, Equation (1.15) provides an estimate for (s2)1 2 of 43 A. This value is several times larger than the value (= 10 A) expected for the same collection of atoms if they were arranged into the most compact globule consistent with the density of liquid rc-alkanes. 

Here v is the partial specific volume and L is Avogadro s number. A similar conclusion is obtained for virtually all unperturbed linear chains (j2)0 is much larger than the result expected for a compact globule. 

As already stated hydrophobic interactions32,33) forcing the particles to coil up into compact globules, play an essential role in the stabilization of the polymer complex particles in water. 

When w decreases beyond wF, the exponent v(w) quickly diminishes and becomes even smaller than the value v = 2/3 which corresponds to a compact globule, but this fact is not significant it shows only that for the corresponding values of v(w), one remains far from the asymptotic regime. Besides, it is expected that in the asymptotic regime v(w) vary discontinuously and not continuously, with respect to w. 

Surface-active materials consist of molecules containing both polar and nonpolar portions, i.e., amphiphilic molecules. The proteins are typically amphiphilic, polymeric substances made of amino acid residues combined in definite sequences by peptide bonds (primary structure). In many cases polypeptide chains are present in helical or /3-sheet configuration (secondary structure) which are stabilized by intramolecular (S-S and hydrogen) bonding. The next structural level, the tertiary structure, is determined by the folding of the polypeptide chains to more or less compact globules, maintained by hy-... 

A reversible transition from a swollen to unperturbed coil and further to a more compact globule-like conformation of polystyrene on cooling its diluted solutions in cyclohexane below the -temperature is well documented by viscosimetric measurements [142, 144], determination of... 

The dimensions of a linear macromolecule in different states have been considered [51]. The following states are known [51, 52] to he the most typical 1 - compact globule, 2 - coil at the 0-point, 3 - impermeable coil in a good solvent, 4 - permeable coil (the state typical of rigid-chain macromolecules), 5 - completely uncoiled rod-like macromolecule. 

FIGURE 100 The dependences of macromolecular coil fractal dimension on beams number/for PS-Cj without flexible junction (1) and with flexible junctions -Si(CHj)- (2), -(CHj/- (3). The horizontal stroked lines indicate values for coil in good solvent (4), 9-solvent (5) and compact globule (6) in a branched polymers case. 

The Eq. (177) physical significance is obvious the smaller parameter e or the stronger interactions of a macromolecular coil elements between themselves, is the lower mobility (freedom) of the indicated elements or the smaller their size is. At e=-0,333, that corresponds to Dj.=3.0 or compact globule, m=0. In other words, the dense package defines suppression of all fragments with arbitrary mobility [225],... 

The authors [228] supposed, that for dendrimers the exponent value was equal to about zero, that corresponds to D=d=3>.Q, that is, to compact globule [25]. However, in Ref [230] it has been shown that for dendrimers of the third generation o =0.24 or D=2A2 according to the Eq. (4). As it is known through Ref [180], the fectal object density p is determined according to the equation (a more precise variant of the equation (139)) ... 

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