Helix, length

Ballesteros, J. A. and Weinstein, H. (1992) The role of Pro/Hyp-kinks in determining the transmembrane helix length and gating mechanism of a Leu-zervamicin channel. Biophys. J. 62,110-111. 

As noted by Bloomfield, Crothers, and Tinoco however, there is value in re-expressing the molar concentrations of each strand in terms of the number of sequence repeats, where a total double-helix length of Tbase pairs, broken into fragments of length L, may contain ni copies of repeat sequence-/. In this way, one can designate the concentration of strands having sequence-/ as [A]/, and [B]/, which in turn can be defined with respect to their nucleotide content ... 

Initial construct screening implemented the sequence space approach that we described above. Four lysine riboswitches from the Rfam database were considered from the following organisms T. maritima, Haemophilus influenzae, E. coli, and B. subtilis. Due to the rigidity in helix length in P2, P3, and P4 hehces, helix variants in the PI and P5 hehces were made (Fig. 6.2B). 

B) The different helix variants used in our initial crystallization library are shown for PI andP5 (highlighted in red). (C) A crystal from a PI helix length of six and P5 helix of four. 

Among non-aggregated molecules and polymers, annelated jr-conjugated molecules such as [njhelicenes possess relatively large optical rotations [21]. Notably, specific rotations of helicenes and thiahelicenes increase significantly with the helix length for (—)-[6]-, -[7]-, -[8]-, -[9]-, -[11]- and-[13]helicenes in chloroform,... 

Helix Length. One property of exchangeable apolipoproteins that must be explained is their ability to target specific lipoprotein particles e.g., apoA-I associates almost entirely with HDLs, which have a smaller radius of curvature than other lipoproteins. ApoE associates invariably... 

The immediate vicinity of a solid phase may strongly affect the activity of the enzyme. The substrate partitions between the fluid phase and the charged polymer solid phase. This can be attributed to the ionic charges and to the limitation of diffusion of the solute to the solid phase due to an unstirred layer of about 1 xm (i.e., corresponding to a double-helix length of about 3000 bp or to more than 100 times the diameter of an average protein) (Trevan, 1980). 

The peptide dipole is aligned nearly parallel to the hehx axis and the strength of the electric field created by the dipole increases up to a helix length of about 10 A (two turns). Thereafter further elongation in the hehx has only a marginal effect. 

The optical activity of helical segments in proteins can vary considerably with helix length, conformation and nature of side chains. The Cotton effects at 198 and 207 mn are sensitive to hehx geometry, while the 233 nm Cotton effect is not, therefore [m]233 measurement gives better average helical contents than do measurements at other wavelengths. The ORD of perfect helices should be relatively independent of solvent because the tightly packed hehx structure provide the uniform local environment for the n tt transition, while distorted hehces will be more environment dependent. 

Figure 1.12 plots z, 0, v, and the mean helix length f = 6/v as functions of the temperature. Temperature is measured in terms of in s (T). The CH transition takes place at around Ins = 0. The transition becomes sharper for a smaller nucleation parameter a (stronger cooperativity). The transition also becomes sharper with molecular weight, and becomes a real phase transition with discontinuous 6 in the limit of infinite chain length. 

Fig. 10.25 (a) Theoretical helix content 9 (solid lines), number of helices v (dotted lines), mean helix length... 

There are a number of small peptide-forming channels. One of the most studied is gramicidin. Gramicidin is a mixture of similar pentadecapeptides containing alternating D- and L-amino acids. These peptides can form a helix with an internal diameter of around 4 A. The helix length is approximately half of the membrane width and, upon being dimerization stabilized by tail to tail interactions, they form... 

Figure 13. Self-assembly of tobacco mosaic virus (TMV). The protein subunits define the shape of the helix and the RNA defines the helix length. All information for assembly is contained within the component parts.

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