Apparent molecular length

Similarly the longitudinal correlation length in molecular position can be measured from the meridional spread of the small-angle scattering maximum arising from smectic-like fluctuations (FIGURE 5). The position Qo of such a peak has been used to estimate the apparent molecular length. 

The molecular length of both compounds in the crystalline state is 19.6 A. X-ray investigations in the nematic phase of NCS5 showed that dimeric (29.3 A) as well as monomeric (18.6 A) units exist. For SCN5, a value of 21.3 A was obtained for the apparent length of the molecules in the nematic phase [108]. 

There are 17 human type I IFN genes, all clustering on chromosome 9. They are intronless and encode secretory signal peptide sequences that are proteolytically cleaved prior to secretion from the cell. Type I IFNs are genetically and structurally closely related. They range in length from 161 to 208 amino acids and have apparent molecular weights of 15-24 kDa (Table 1) (Chen et al. 2004). The different subtypes of human IFN-a have approximately 50% amino acid sequence identity, whereas IFN-a shares approximately 22% amino acid identity with human IFN-p and 37% with human IFN-m (Chen et al. 2004). 

The method of equilibrium ultracentrifugation described by Yphantis (28) was used in these studies. A double-sector centerpiece with two 2 1/2° sectors 12 mm. in length was used with standard Schlieren optics. Apparent molecular weights, M, were determined from the equation ... 

Fig. 11(a) shows the AFM image of an 11-layer mixed-stack CT film of octadecyl-TCNQ and (Me)2P scanned at room temperature with a scan area of 2x2 pm2 [29]. It can be seen from the image that the CT film consists of platelet microcrystal domains of a few micrometers in size in which a multi-layered structure with many steps is observed. An analysis of the cross-sectional profile revealed that the layered platelet microcrystal domains have a step of 3.3 nm thickness [29]. This is in good agreement with the d value measured by the X-ray diffraction method [28]. Therefore, it seemed that the X-ray diffraction peaks originate from the multi-layered structure inside the domains. Each layer in the domains apparently consists of biomolecular layers of octadecyl-TCNQ and (Me)2P because the layer thickness of 3.3 nm is larger than the molecular length (3.0nm) of octadecyl-TCNQ. The biomolecular layer structure also supports that the CT film is in a mixed-stack pattern. 

Coulson CA, Thomas MW (1971) The effect of molecular vibrations on apparent bond lengths. Acta Cryst B27 1354-1359... 

In naphthalene and other polycyclic aromatic hydrocarbons apparent bond lengths become shorter, especially when they are more distant from the molecular center. When corrected for effects of rigid-body libration, this trend disappears. Studies of naphthalene, anthracene, and 4-hydroxybiphenyl illustrate this. In naphthalene... 

ApoB size is expressed in the centile nomenclature, which indicates the apparent molecular weight, as determined by SDS-PAGE as a percentage of the molecular weight of the full-length apoBlOO. 

Absence of surface interactions that effect the conformation of the macromolecules is, however, not the rule. Below we will discuss examples of how the molecular conformation can be effected by specific interaction with the substrate. Obviously, one cannot regard the apparent persistence length of the adsorbed molecules as a characteristic value for the chain flexibility. 

Myosin is another protein to which the theory of Linderstr0m-Lang in its present form is not applicable, since in myosin the ratio of molecular length to width is 100/1—far from the sphericity on which the theory is based. Thus experimental values of the parameter w cannot be easily interpreted quantitatively. Myosin is soluble in the presence of salt on the alkaline side of its isoionic point only, and thus should behave as a soluble protein above pH 5.7 to 5.8 and as an insoluble one below this. Mihdlyi (1950) has studied the effect of salt on the titration of myosin and reports that its insolubility in acid in the presence of greater than 0.05 M KCl does not affect the reversibility of the titration nor are there any obvious discontinuities in his titration curves, shown in Fig. 4. The data for basic solutions appear to be affected by salt very much as those of other soluble proteins, and reach an apparent limiting curve at a fairly low ionic strength (0.15). In acid solution where the protein is insoluble, however, the effect of salt closely resembles that for wool, except that the displacements of the parallel central portions of the curves are somew hat less than for wool, consistent with a lower affinity of myosin for chloride ion. The slopes of these portions of the curves are within 10 % of those observed for... 

Ghosh S, Li X, Reed CE, Reed WF. Apparent persistence lengths and diffusion behavior of high molecular weight hyaluronate. Biopolymers 1990 30 1101-1112. 

It should be noted that in QCM measurement interfacial properties are determined by averaging over the length scale S. As a result one cannot distinguish between a true slip on the molecular level and an apparent hydrodynamic slip, which can arise from a shear thinning of the hquid near the surface. The latter leads to a steep velocity profile at the surface that appears as a slip, although the velocity is continuous at the surface. Indeed, a comparison between Eqs. 19-20 and Eqs. 16-17, which describe the effects of slip and surface film on the resonant frequency respectively, allow a relationship to be established between the apparent shp length and the film properties that give the same QCM response ... 

The liquid crystals, in fact, meet the above requirements large molecular length, linear molecular configuration and with polar terminals. Unfortunately, low molecular mass liquid crystals have difficulty in maintaining the non-center symmetry after electrical polarization. Moreover, it is difficult to process the low molecular mass liquid crystal materials. Apparently, polymers are good candidates in these respects. 

Prasad (1988) further demonstrated that 7 increases remarkably with the increase of the molecular length n. The relation of 7 and n of the para-acetylene (C H +2) is shown in Figure 6.35 in which 7 increases exponentially with n. Therefore, the long molecular shape and the linear conjugated system are still the essential requirements for a high x 3" -Apparently, liquid crystals are a good candidate. 

---