Chain forms of Factor

Factor XIII is present in both plasma and platelets. Plasma factor XIII is a 320 kDa tetramer, composed of two (70 kDa) a-chains, and two (90 kDa) /i-chains. The platelet form of factor XIII... 

The mature form of Factor X consists of a 139-residue fight chain and a 303-residue heavy chain finked by a sulfide. It is synthesized in the fiver... 

The complete structural elucidation of 110 by means of spectroscopic methods and biogenetic considerations was not accomplished until Battersby et al (68) and Bykhovsky et al (69) were able to isolate factor II (sirohydrochlorin) (108) from bacteria producing vitamin B12. Factor II (108) is the metal-free isobacteriochlorin chromophore of siroheme. The reduced forms of factor II (108) and of the subsequently discovered factor III (109) were identified, together with factor I (65), as the first links in the biosynthetic chain from uroporphyrinogen III (14) to vitamin B12 (4) (11). The vitamin B12 biosynthesis will be dealt with in more detail in a later section (see section 9). Factor III (109) differs from factor II (108) by virtue of an additional methyl group in the methine position 20. 

Figure 6. Schematic representation of the cDNA percursors which give rise to the mature two-chain forms of human factor X (lOI-106) and human protein C (107-109) found in plasma. The 5 and 3 untranslated regions of the mRNA are represented by the slashed bars, the leader peptides are represented by the shaded bars and the sequences encoding the mature plasma protein are represented by the open bars. The basic amino acid residues released on conversion of the two-chain forms of the proteins are denoted by the arrows, and the catalytic triad is indicated by H, D and S. The scale represents 100 bp.

Inhibin and Activin. Inhibin, a water-soluble, gonadal factor known for over 50 years to inhibit pituitary function, has been isolated and identified (127—130). Inhibin is a glycoprotein hormone that preferentially inhibits the secretion of FSH. It consists of an a-chain subunit, mol wt 14,000, linked by disulfide bonds to a P-chain subunit, mol wt 18,000. There exist two forms of the P-chain subunit, P-A and P-B. The smaller subunit combines with either the P-A or P-B subunit to form inhibin-A or inhibin-B, respectively. 

The glass transition temperature of a random copolymer usually falls between those of the corresponding homopolymers since the copolymers will tend to have intermediate chain stiffness and interchain attraction. Where these are the only important factors to be considered a linear relationship between Tg and copolymer composition is both reasonable to postulate and experimentally verifiable. One form of this relationship is given by the equation... 

The above-mentioned models differ in the relation that is derived between the rate of pull-out of the individual chain and the crack velocity. These models also differ in their interpretation of the threshold stress and the threshold toughness (Go). Also, V is expected to be dependent on the configuration of the connector chain at the interface. The value of v when connector chain crosses the interface just once is higher than the value when the chain forms multiple stitches, even though Go is not altered. When the chain forms multiple stitches, the block and tackle effect ensures that the viscous processes dominate even at lower velocities, and V is reduced by a factor of N from the value obtained from the single crossing case. These models are discussed by Brown and coworkers [45,46]. 

There are additional factors that may reduce functionality which are specific to the various polymerization processes and the particular chemistries used for end group transformation. These are mentioned in the following sections. This section also details methods for removing dormant chain ends from polymers formed by NMP, ATRP and RAFT. This is sometimes necessary since the dormant chain-end often constitutes a weak link that can lead to impaired thermal or photochemical stability (Sections 8.2.1 and 8.2.2). Block copolymers, which may be considered as a form of end-functional polymer, and the use of end-functional polymers in the synthesis of block copolymers are considered in Section 9.8. The use of end functional polymers in forming star and graft polymers is dealt with in Sections 9.9.2 and 9.10.3 respectively. 

It will be noted from the preceding discussion that impurities may induce more than one form of corrosion. The particular types of corrosion and the influence of these impurities work in a developing chain of cause and effect, depending in large part on the specific operating circumstances in question. Such factors include the boiler system basic configurational design, the localized areas of stress, and the temperature of various metal surfaces. 

Most biological polymers, such as proteins and nucleic acids and some synthetic polymers, have relatively inflexible chains. For rigid particles, the size is no longer of predominant importance, because the polymer chain is no longer in the form of a flexible random coil instead, shape becomes an important parameter. Following are some theoretical proposals for the estimation of the shape factor p from the viscosity measurement (table 4). The term f/fo is sometimes denoted as p, Perrin constant. 

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