Induced rigidity

In Section II, we shall briefly recall the statistical mechanics of the helix-coil transition for isolated chains. We shall then present an argument showing that there is little tendency for non-interacting molecules to exhibit substantial mesomorphic fluctuations. A mean field theory for incorporating the interchain interactions will be developed in Section III in the cooperative limit for helix-coil transition. Some final remarks will be made in Section IV. 

The helix-coil transition of a polypeptide chain consisting of N monomers is usually described in terms of two parameters  

Small values of the cooperativity parameter, E, favor sharp helix-coil transitions which necessarily have very few segments. In terms of these parameters, the free energy per macromolecule may be simply written as 

The role of E in determining the sharpness of the transition may be graphically seen by considering the persistence length, V, which is the average number of monomers per helical segment. 

The (N/v) rigid segments are then confined to a volume of order, giving a rod density 

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Diamond and coworkers attribute an increase in fluorescence from the anthracene reporter sites of 44 to the increased rigidity induced by complexation of Li+, Na+, and K+ to the calixarene s tetraester cleft. The tetraamide derivative, 45, shows an especially selective response to Na+ ion [383], Restricted motion of the calix[4]arene is believed to lead to the enhanced luminescence response. This contention is supported by H NMR studies, which show metal ions to confer significant order on the calix[4]arene receptor. 

Whether treatment with olanzapine is useful in psychotic symptoms in patients with Parkinson s disease is unclear (SEDA-23, 66). Nine patients of twelve with drug-induced psychosis in Parkinson s disease had worsening of motor function while taking olanzapine (2.5 mg/ day and increased in 2.5 mg increments as needed) this worsening was considered dramatic in six of these patients, and only one was still taking olanzapine at the time of the analysis (12 months) (116). In addition, two elderly patients, one with and one without pre-existing parkinsonism, had marked rigidity induced by olanzapine 5 mg/day (117). 

The rigidity produced in untreated monkeys by a-methyldopa can be transiently reversed by L-dopa as can the tremor in lesioned monkeys [577]. Apomorphine also rapidly alleviates reserpine-induced tremor, while both it and ( + )-amphetamine reverse the reserpine rigidity. Benztropin has a favourable effect on tremor and rigidity induced by drugs or by the lesions. Intrastriatal injection of mescaline to rats also produces motor disturbances characterised by tremor, choreiform movements, and other dyskinesias [578]. 

Fig. 2. Principle mechanisms of formation of a receptor—substrate complex (a) Fischer s rigid "lock-and-key" model (b) "induced fit" model showing...

LB Films of Polymerizable Amphiphiles. Stxidies of LB films of polymerizable amphiphiles include simple olefinic amphiphiles, conjugated double bonds, dienes, and diacetylenes (4). In general, a monomeric ampbipbile can be spread and polymerization can be induced either at tbe air—water interface or after transfer to a soHd substrate. Tbe former polymerization results in a rigid layer tbat is difficult to transfer. 

The referential formulation is translated into an equivalent current spatial description in terms of the Cauchy stress tensor and Almansi strain tensor, which have components relative to the current spatial configuration. The spatial constitutive equations take a form similar to the referential equations, but the moduli and elastic limit functions depend on the deformation, showing effects that have misleadingly been called strain-induced hardening and anisotropy. Since the components of spatial tensors change with relative rigid rotation between the coordinate frame and the material, it is relatively difficult to construct specific constitutive functions to represent particular materials. 

The deformation may be viewed as composed of a pure stretch followed by a rigid rotation. Stress and strain tensors may be defined whose components are referred to an intermediate stretched but unrotated spatial configuration. The referential formulation may be translated into an unrotated spatial description by using the equations relating the unrotated stress and strain tensors to their referential counterparts. Again, the unrotated spatial constitutive equations take a form similar to their referential and current spatial counterparts. The unrotated moduli and elastic limit functions depend on the stretch and exhibit so-called strain-induced hardening and anisotropy, but without the effects of rotation. 

Molecules do not consist of rigid arrays of point charges, and on application of an external electrostatic field the electrons and protons will rearrange themselves until the interaction energy is a minimum. In classical electrostatics, where we deal with macroscopic samples, the phenomenon is referred to as the induced polarization. I dealt with this in Chapter 15, when we discussed the Onsager model of solvation. The nuclei and the electrons will tend to move in opposite directions when a field is applied, and so the electric dipole moment will change. Again, in classical electrostatics we study the induced dipole moment per unit volume. 

Gearboxes must be installed on a rigid base that prevents flexing of its housing and the input and output shafts. Both the input and output shaft must be properly aligned, within 0.002 inch, to their respective mating shafts. Both shafts should be free of any induced axial forces that may be generated by the driver or driven units. 

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