Protein chain thickness

AHAs do not coagulate proteins. Applying them in a peel should not therefore produce a whitening elfect . According to Forestier, the mechanism of action of AHAs is as follows. Even at low concentrations, AHAs can insert themselves between two protein chains. Here, they build a sort of bridge that reduces corneocyte cohesion. As a result of the lytic action of AHAs on corneodesmosomes, corneo-cytes are shed more easily from the skin, and the thickness of the stratum corneum is reduced. The skin appears more hydrated as the stratum corneum is thinned or disappears temporarily. 

Figure 1.18 Comparison of the deletions detected in variants of human H chains and tentative classification. On top are represented the domains and disulphide bridges of normal y and a chains. Thick lines indicate the position of the hinge region. Dotted lines localize the deletions. Normal sequences after internal deletions start at the indicated residues. For the sequence of yl, y2, y3, and y4 variants, see Table 1.8b, and for protein DBF, see Figure 1.14.

Each thick filament is composed of about 250 myosin molecules. Myosin has two important roles a structural one as the building block for thick filaments and a functional one as the catalyst of the breakdown of adenosine triphosphate (ATP) during contraction and its interaction with actin as part of the muscle force generator. Actin is an important constituent of the thin filament. The molecular mass of myosin is about 500000 it contains two major protein chains and four small ones, the entire molecule being about 160 nm long, and has a coiled-coil structure. The interaction of actin and myosin provides a basis for molecular models of force generation and contraction in living muscle. 

Contractile proteins which form the myofibrils are of two types myosin ( thick filaments each approximately 12 nm in diameter and 1.5 (im long) and actin ( thin filaments 6nm diameter and 1 (Am in length). These two proteins are found not only in muscle cells but widely throughout tissues being part of the cytoskeleton of all cell types. Filamentous actin (F-actin) is a polymer composed of two entwined chains each composed of globular actin (G-actin) monomers. Skeletal muscle F-actin has associated with it two accessory proteins, tropomyosin and troponin complex which are not found in smooth muscle, and which act to regulate the contraction cycle (Figure 7.1). 

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