Random coil, structure

The availability of the purified transporter in large quantity has enabled investigation of its secondary structure by biophysical techniques. Comparison of the circular dichroism (CD) spectrum of the transporter in lipid vesicles with the CD spectra of water-soluble proteins of known structure indicated the presence of approximately 82% a-helix, 10% ) -turns and 8% other random coil structure [97]. No / -sheet structure was detected either in this study or in a study of the protein by the same group using polarized Fourier transform infrared (FTIR) spectroscopy [98]. In our laboratory FTIR spectroscopy of the transporter has similarly revealed that... 

The cahnodulin-binding peptides assume random coil structures in solution, but in the presence of calmodulin they form amphipathic or amphiphilic (containing both polar and nonpolar residues) helices. All of these peptides have nanomolar (very high) affinities for calmodulin. Table 6.9 shows the primary amino acid sequence of some of the cahnoduUn-binding peptides, and it is informative to compare them as they are discussed in the following material. 

Perhaps the most viable short-term use for dendritic macromolecules lies in their use as novel catalytic systems since it offers the possibility to combine the activity of small molecule catalysts with the isolation benefits of crosslinked polymeric systems. These potential advantages are intimately connected with the ability to control the number and nature of the surface functional groups. Unlike linear or crosslinked polymers where catalytic sites may be buried within the random coil structure, all the catalytic sites can be precisely located at the chain ends, or periphery, of the dendrimer. This maximizes the activity of each individual catalytic site and leads to activities approaching small molecule systems. However the well defined and monodisperse size of dendrimers permits their easy separation by ultrafiltration and leads to the recovery of catalyst-free products. The first examples of such dendrimer catalysts have recently been reported... 

The random coil structure has no repeating geometric pattern encompassed within it are sequences in a helical conformation, a pleated conformation, and regions that appear to have no discernible repeating structure, but are actually not random conformation. 

Whilst the dichroic properties of fully reduced 6 in aqueous buffer (pH 9.5) are typical of a random coil structure, addition of TFE leads to a CD spectrum that indicates an increased content of a-helical structure as its pattern becomes similar to the CD spectrum of 6 in 50% TFE at pH 7.0.[451 These results confirm that induction of a-helical conformation by addition of TFE is responsible for the observed increased content of the native isomer 1. 

On the other hand, the deposition process is also important to prepare blend samples. A mixture of homopolypeptide solutions in which they take a random coiled structure are added into a poor solvent. For polypeptides, water is a poor solvent in general. If the hydration rate is different for each polypeptides, they form their preferred secondary structures by themselves and then do not blend with each other. On the basis of this assumption, in order to make the hydration at the same time, the solution is added to alkaline water. In this review, two kinds of quieting solvents such as water and alkaline water have been used. (Methods 1-4 and Method 5). Method 1 Helical polypeptide and (3-sheet polypeptide are dissolved in DCA and agitated... 

High molecular weight and random coil structure of protein result in more associations and thereby enhance adhesive and cohesive properties. Although these characteristics are inherent in native gluten proteins, functional properties of other proteins may be improved by chemical or thermal processing. 

Chelation of 32 with the 17-residue peptides 33 and 34 (Scheme 20) results in up to 80 and 50% helix, respectively, at 21 °C, as measured by CD spectroscopy. Without the metal complex, 33 is 45% helical, while uncomplexed 34 exhibits the CD spectrum of a random coil structure.11771 Helix induction results from the loss of conformational flexibility of the peptides upon complexation. 

The IR studies of Idelson and Blout (53) demonstrated that in dioxane the initially-formed polymer possessed a random-coiled structure (described by the authors as the /3-form). As the reaction proceeded a new material appeared, which was identified through its IR spectrum as the a-helix. This stage of the process coincided with the onset of a fast reaction. By using a deuterated n-hexyl amine as the initiator a labelled /S-peptide was prepared. This was used in turn to initiate further polymerisation which yielded an a-peptide. The isolation of the latter and its analysis proved that the a-peptide contained the expected percentage of deuterium, and hence the /S-polymer had to be the precursor of a-peptide. 

The fold of a protein is the way in which the regions of helix, strand and random-coil structure within its polypeptide chain are arranged in three dimensions to form its tertiary structure (see Sect. 2.1.3). This is the simplest, and yet often a very revealing, level at which the three-dimensional structures of different proteins can be compared with one another as is indicated below, such similarities may be indicators of remote evolutionary relationships, give clues to functional analogies, or insights into the processes of protein folding. 

For example, classes of natural products in which conformational fixation is very important are the peptides and proteins. They can adopt different secondary structures by intra- and/or interstrand hydrogen bonding, ranging from helical or sheet-type structures (with the most prominent being the a-helix or the /i-shcct - Box 8) to different turn (e.g. y-turn) or random coil structures (Figure 1.3.1) [1]. 

Contributions of / -sheet structures to the spectra were not found to be present. It was concluded that the PLL conformation in the PEO-PLL18 retinoate and PEO-PLL30 retinoate micelles adopts an a-helix for pH values higher than 9.0 and a random coil at a pH lower than 3.7, while between these limiting values a mixture of a-helical and random coil structures is present. 

Random Coil Structures. The term "random coil" may be a misnomer. When proteins are unfolded, it is still unclear whether the structure of the denatured protein is truly random. Terms such as unordered or other, are often used to refer to the random coil state. The CD of denatured proteins or small peptides displays one dominant feature, a strong... 

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