The Plasma Proteins and Their

The Plasma Proteins and Their Fractionation John T. Edsall... 

Peptide-hormones like hypothalamus-pituitary, gastrointestinal, parathyroid, neurohormones, Gfs related peptide-hormones cannot penetrate the plasma membrane and their receptors are located on the cell surface and the signal transport to the nucleus is becoming via a second messenger. The main hormone action seems to be DNA synthesis whereas other including mediation of neurotransmission, enzyme synthesis, regulation and synthesis of structural proteins are responsible for the specific characteristics of differentiated cell. 

Table 20-3 lists the principal plasma proteins and their half-lives, pi, molecular weights, and preferred method of analysis the individual proteins are listed in the order of their electrophoretic mobilities in agarose gels at pH 8.6. These proteins are described later in this chapter other chapters in this book describe many more proteins enzymes (see Chapter 21) lipoproteins (see Chapter 26) hormones (see Chapter 28) and hemoglobin, fibrinogen, and other coagulation proteins (see Chapter 31). The interim consensus reference intervals for 14 plasma proteins are listed in Table 20-4, pending the publication of more definitive intervals. . 

Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), which has been successfully used to establish a correlation between adsorbed proteins and in vivo behavior of polystyrene carriers coated with Poloxamers (Blunk etal, 1994) could be a helpful tool to study competitive plasma protein adsorption on PEG-coated nanospheres as a function of PEG chain length and surface density. Indeed, the relevance of the adsorbed plasma proteins (and their ratios and conformations) with respect to the in vivo fate of the particles remains to be uncovered. 

In addition to binding to sialic acid residues of the carbohydrate side chains of cellular proteins that the virus exploits as receptors, hemagglutinin has a second function in the infection of host cells. Viruses, bound to the plasma membrane via their membrane receptors, are taken into the cells by endocytosis. Proton pumps in the membrane of endocytic vesicles that now contain the bound viruses cause an accumulation of protons and a consequent lowering of the pH inside the vesicles. The acidic pH (below pH 6) allows hemagglutinin to fulfill its second role, namely, to act as a membrane fusogen by inducing the fusion of the viral envelope membrane with the membrane of the endosome. This expels the viral RNA into the cytoplasm, where it can begin to replicate. 

Protein trafficking is the transport of proteins to their correct subcellular compartments or to the extracellular space ( secretory pathway ). Endo- and exocytosis describe vesicle budding and fusion at the plasma membrane and are by most authors not included in the term protein trafficking. Protein quality control comprize all cellular mechanisms, monitoring protein folding and detecting aberrant forms. 

Biomedical Applications Due to their excellent blood compatibility (low interaction with plasma proteins) and high oxygen and moisture permeabilities, siloxane containing copolymers and networks have been extensively evaluated and used in the construction of blood contacting devices and contact lenses 376). Depending on the actual use, the desired mechanical properties of these materials are usually achieved by careful design and selection of the organic component in the copolymers. 

Thus far, microtubules and actin filaments and their associated proteins have been discussed to advantage as independent cytoskeletal components. In actual fact, all of the components of the cytoskeleton (including intermediate filaments) are precisely integrated with one another (Langford, 1995), as well as with various cytoplasmic organelles, the nuclear membrane, the plasma membrane, and the extracellular matrix. In its totality the cytoskeleton subserves many coordinated and regulated functions in the cell ... 

More is known about nitrogen. In a study of modern humans where diet components (protein, lipid and carbohydrate) were measured against the corresponding body components, a shift of between 4.2 and 4.4%o was observed for nitrogen in both plasma protein and hair (Schoeller et al. 1986). This is just outside the usual 3-4%o range. Salmon fishers from coastal British Columbia are enriched by 3%o compared to their diet (Chisholm et al. 1983). Ancient Mexicans have constant 8 N values, as reported by DeNiro and Epstein (1981) 8-10%o, and While and Schwarcz (1989) 9.8 0.8%o. In the latter... 

The intraocular pressure depends primarily on the rate of secretion of aqueous humour. The most notable con-stititutional difference between aqueous humour and blood plasma lies in their protein contents. Protein concentration in the aqueous is 5-15 mg/100 ml, and that of the plasma is 1000-fold greater (6-7 g/100 ml). However, all the plasma proteins are present in aqueous humour - albeit at very low concentrations, therefore it is... 

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