Electrostatic propensity

Tests Simulating Use Conditions. Several simulation tests involving wear and use testing have been developed. The first and only one to be adopted as a standard in the United States is AATCC Test Method 134-1975 for measuring the electrostatic propensity of carpets (60). In this test a person wearing standard neoprene and leather sole shoes and carrying a probe connected to an electrometer walks on a carpet for 30 to 60 s until the measured body voltage builds up to a maximum. 

A technique for the measurement of the electrostatic propensity of textile filaments can be found in ASTM D 4238-90. 

The electrostatic propensity of a textile polymer is defined in ASTM D 4238 as the capacity of a nonconducting material to acquire and hold an electrical charge by induction (via corona discharge) or by triboelectric means (i.e., rubbing with another material). 

ASTM D 4238 90—Test Method for Electrostatic Propensity of Textiles... 

Gonzalez JA, Rizvi SA, Crown EM, Smy P. A laboratory protocol to assess the electrostatic propensity of protective clothing systems. J Textil Inst 2001 92(l) 315-27. 

Electrostatic propensity Excellent Excellent Poor to very good... 

Fig. 2.16 Effect of electrostatic interactions on 3i4-helix formation in an aqueous environment [1 75 a, 175 b, 176]. y -Peptides 86 and 87 adopt a stable helical conformation mediated by salt bridges near neutral pH. While the propensity of these peptides to adopt a helical conformation is strongly de-...

Sidechain conservatism may be split up into at least two kinds 1) substitutions which conserve sidechain bonding forces - providing similar electrostatic, hydrophilic, or hydrogen bonding interactions, and 2) substitutions conserving secondary structure propensity. For instance, substitution of glutamic acid with aspartic acid conserves charge, but this could have a considerable effect upon the secondary structure propensity of the peptide. 

Retention in HIC can be described in terms of the solvophobic theory, in which the change in free energy on protein binding to the stationary phase with the salt concentration in the mobile phase is determined mainly by the contact surface area between the protein and stationary phase and the nature of the salt as measured by its propensity to increase the surface tension of aqueous solutions [331,333-338]. In simple terms the solvopbobic theory predicts that the log u ithn of the capacity factor should be linearly dependent on the surface tension of the mobile phase, which in turn, is a llne2u function of the salt concentration. At sufficiently high salt concentration the electrostatic contribution to retention can be considered constant, and in the absence of specific salt-protein interactions, log k should depend linearly on salt concentration as described by equation (4.21)... 

This bistability is favoured by structures, which will adopt n—stacked motifs, i.e. lamellar molecules. In addition the tendency to adopt the planar structure is enforced by the presence of electronegative heteroatoms (currently restricted to N), which lead to a propensity of in-plane electrostatic S- N contacts between rings. These may comprise heterocyclic S- N contacts or S- N contacts to other functional groups such as the pyrazine or cyano nitrogen atoms. 

Applications are curbed by low rigidity, weak HDTs and melting points, a propensity for electrostatic and dust build-up, poor creep resistance, limited resistance to acids, a certain lack of sources, and the cost. 

Effect of salt type and concentration The ionic strength of the aqueous solution in eontaet with a reverse micelle phase affects protein partitioning in a number of ways [18,23]. The first is through modification of electrostatic interactions between the protein surface and the surfaetant head groups by modifieation of the eleetrieal double layers adjacent to both the eharged inner mieelle wall and the protein surface. The second effect is to salt out the protein from the mieelle phase because of the inereased propensity of the ionie speeies to migrate to the micelle water pool, reduee the size of the reverse mieelles, and thus displace the protein. 

Scheme 2 shows a cross-sectional representation of a two-stranded a-helical coiled coil of 35 residues per polypeptide chain. The design of this idealized coiled coil incorporated the factors that maximize coiled-coil stability, for example, the hydrophobicity and packing effects in the hydrophobic core, intrachain electrostatic attractions, helical propensity contribution s[2324 from residues outside of the hydrophobic interface, and interchain electrostatic interactions.125 ... 

As long ago as 1984, Lau et al.1311 demonstrated that stable coiled coils of four heptads in length could be formed. Subsequent work set out to examine the factors that would maximize stability of the coiled coil in the shortest possible chain length, for example, hydro-phobicity and packing effects in the hydrophobic core, intrachain electrostatic interactions, and the helical propensity contribution of residues outside the hydrophobic interface.123,24 30 321... 

Any compd or mixt whose heat of formation is smaller by 500 J/g (or more) than the sum of the heats of formation of its reaction products must be regarded with suspicion and handled with more than usual care. The hazards involved in working with a potentially expl system are directly proportional to the amount and to the rate of energy release. Because the reaction kinetics cannot be predicted, the propensity of a new system for expl reaction must be determined. The sensitivity of the system can be evaluated by means of impact, friction, shock and electrostatic discharge. Appropriate methods are reviewed in the Experimental and Hazard Assessment section of this article. Sensitivity to heat or elevated temp may be evaluated by use of differential thermal analysis (DTA)... 

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