And molecular defects

Rabe J P, Sano M, Batchelder D and Kalatchev A A 1988 Polymers on graphite and gold—molecular images and substrate defects J. MIcrosc. 152 573-83... 

Chain transfer is an important consideration in solution polymerizations. Chain transfer to solvent may reduce the rate of polymerization as well as the molecular weight of the polymer. Other chain-transfer reactions may iatroduce dye sites, branching, chromophoric groups, and stmctural defects which reduce thermal stabiUty. Many of the solvents used for acrylonitrile polymerization are very active in chain transfer. DMAC and DME have chain-transfer constants of 4.95-5.1 x lO " and 2.7-2.8 x lO " respectively, very high when compared to a value of only 0.05 x lO " for acrylonitrile itself DMSO (0.1-0.8 X lO " ) and aqueous zinc chloride (0.006 x lO " ), in contrast, have relatively low transfer constants hence, the relative desirabiUty of these two solvents over the former. DME, however, is used by several acryhc fiber producers as a solvent for solution polymerization. 

NIDDM is a much more common disease than IDDM, accounting for about 85—90% of all cases of diabetes meUitus. Whereas NIDDM may be present at any age, the incidence increases dramatically with advanced age over 10% of the population reaching 70 years of age has NIDDM. Patients with NIDDM do not require insulin treatment to maintain life or prevent the spontaneous occurrence of diabetic ketoacidosis. Therefore, NIDDM is frequendy asymptomatic and unrecognized, and diagnosis requires screening for elevations in blood or urinary sugar. Most forms of NIDDM are associated with a family history of the disease, and NIDDM is commonly associated with and exacerbated by obesity. The causes of NIDDM are not well understood and there may be many molecular defects which lead to NIDDM. 

To examine the soUd as it approaches equUibrium (atom energies of 0.025 eV) requires molecular dynamic simulations. Molecular dynamic (MD) simulations foUow the spatial and temporal evolution of atoms in a cascade as the atoms regain thermal equiUbrium in about 10 ps. By use of MD, one can foUow the physical and chemical effects that induence the final cascade state. Molecular dynamics have been used to study a variety of cascade phenomena. These include defect evolution, recombination dynamics, Hquid-like core effects, and final defect states. MD programs have also been used to model sputtering processes. 

The actual experimental moduli of the polymer materials are usually about only % of their theoretical values [1], while the calculated theoretical moduli of many polymer materials are comparable to that of metal or fiber reinforced composites, for instance, the crystalline polyethylene (PE) and polyvinyl alcohol have their calculated Young s moduli in the range of 200-300 GPa, surpassing the normal steel modulus of 200 GPa. This has been attributed to the limitations of the folded-chain structures, the disordered alignment of molecular chains, and other defects existing in crystalline polymers under normal processing conditions. 

Shieh CC, Coghlan M, Sullivan JP et al (2000) Potassium channels molecular defects, diseases, and therapeutic opportunities. Pharmacol Rev 52 557-594... 

Alpha-quartz has many useful properties which lead to its wide use in industry as a glass, ceramic and molecular sieve. However, undoubtedly its most technically important use occurs by virtue of its piezo-electric properties, which allow it to be used as a frequency regulating device in satellites, computers, and the ubiquitous quartz-watch . Unfortunately, it has been found that quartz crystals are susceptible to damage by radiation, and that this is associated with the presence of defects in the crystal lattice. These defects, particularly aluminum and hydrogen, are grown into the crystal and so far have proved impossible to remove. This problem has been the cause of intensive research, which has led to some information on the possible types of defects involved, but has failed to produce details of their geometries, and the way in which they interact. 

The nature of the molecular defect Is unclear and presumably lies In the repression mechanism for the gene controlling formation of the enzyme protein. Exposure to any of the drugs listed In Table V results In further marked de-repressIon of enzyme synthesis and severe porphyria. 

Electrophoretic and kinetic studies of the patient s enzyme have been reported in several cases (F10). Most of them showed decreased substrate affinity and abnormal electrophoretic mobility. The main cause of P5N deficiency is considered to be an abnormality of P5N-I, probably arising from a structural gene mutation (H6). The precise molecular defect has not been clarified, because the normal gene for P5N-I has not been isolated. 

Low levels or absence of adenosine deaminase (ADA) is associated with one form of severe combined immunodeficiency disease (SCID) characterized by B-andT-lymphocyte dysfunction due to toxic effects of deoxyadenosine (HI9). Most patients present as infants with failure to thrive, repeated infections, severe lymphopenia, and defective cellular and humoral immunity. Disease severity is correlated with the degree of deoxyadenosine nucleotide pool expansion and inactivation of S-adenosylhomocysteine hydrolase in red blood cells. Up to now, more than 40 mutations have been identified (A4, H20, S5, S6). The majority of the basic molecular defects underlying ADA deficiency of all clinical phenotypes are missense mutations. Nonsense mutations, deletions ranging from very large to single nucleotides, and splicing mutations have also been reported. It is likely that severe... 

B9. Baronciani, L., Zanella, A., Bianchi, P Zappa, M Alfinito, E, Iolascon, A., Tannoia, N., Beutler, E., and Sirchia, G., Study of the molecular defects in glucose phosphate isomerase-deficient patients affected by chronic hemolytic anemia. Blood 88,2306-2310 (1996). 

M2. Maeda, M and Yoshida, A., Molecular defect of a phosphoglycerate kinase variant (PGK-Mat-sue) associated with hemolytic anemia Leu - Pro substitution caused by T/A - C/G transition in exon 3. Blood 77, 1348-1352(1991). 

T26. Turner, G., Fletcher, J., Elber, J., Yanagawa, Y Dav6, V., and Yoshida, A., Molecular defect of a phosphoglycerate kinase variant associated with haemolytic anaemia and neurological disorders in a large kindred. Br. J. Haematol. 91,60-65 (1995). 

Mutations in the antithrombin (AT) gene have been the basis of AT deficiency. In type I AT deficiency the level of circulating protein molecule and activity are reduced to nearly 50% of normal. Molecular defects in the AT gene resulting in gene deletions at specific DNA sequences may be the basis for type I AT deficiency predisposing such patients to thrombosis (82). 

Without going into the molecular defects in other coagulation factors, suffice it to say that our current understanding of mechanisms leading to the clinical expression of thrombosis and bleeding has been enhanced by the knowledge of such mutations. 

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