Positional specificity

Although the continuum model of the ion could be analyzed by Gauss law together with spherical symmetry, in order to treat more general continuum models of electrostatics such as solvated proteins we need to consider media that have a position-specific permittivity e(r). For these a more general variant of Poisson s equation holds ... 

Two different routes to PCs via bicyclo[3.1.0]hexane intermediates are shown. In route 1 stereo- and position-specific addition of dichloroketene to a bicyclo[3.1.0]hexene provided the framework for elaboration to prostanoids. Route 2 featured stereospecific internal cyclopropanation and stereospecific Sn2 displacement of carbon to establish the prostanoid nucleus. 

Within 1 year of the reaction, between 70 and 90% of patients have specific IgE positive to venoms while only between 10 and 20% of people with a negative history have positive test results. The predictive value of skin tests and the determination of specific IgE is not high in that between 55 and 76% of people with positive specific IgE... 

Proteins may be classified on the basis of the solubility, shape, or function or of the presence of a prosthetic group such as heme. Proteins perform complex physical and catalytic functions by positioning specific chemical groups in a precise three-dimensional arrangement that is both functionally efficient and physically strong. 

Puschel, A., Balling, R., and Grass, P. (1990). Position specific activity of the Hox-1.1 promoter in transgenic mice. Development 108 435-442. 

The positional specificity of these nucleophilic and electrophilic photosubstitutions can be readily understood by examination of the calculated charge densities of some of these molecules in their ground and first excited singlet states. For example, 4-nitrocatechol has the charge densities shown in (82) and (83).<139> Thus on this basis one would predict that 4-nitroveratrole... 

Brenna J. T. (2001) Natural intramolecular isotope measurements in physiology elements of the case for an effort toward high precision position specific isotope analysis. Rapid Communications in Mass Spectrometry 15(15), 1252 1262. 

In short, the space within the active site and the orientation of the substrate are both important determinants for the positional specificity of plant LOXs and are modified by additional factors such as substrate concentration, the physicochemical state of the substrate, pH, or temperature (Lopez-Nicolas and others 2000). However, it should be stressed that for other LOXs regiospecificity may be determined in a more complex manner. 

Schoor, W.P. and M. Srivastava, 1984. Position-specific induction of benzo[a]pyrene metabolism by 3-meth-ylcholanthrene and phenobarbital in mullet (Mugil cephalus), a marine fish. Comp. Biochem. Physiol. 73C 391-396. 

That portion below pQ is called the negative phase. Positive specific impulse, defined by... 

In colour vision there are three specific types of cone cell corresponding to red, green and blue receptors. The chromophore is the same for all three colours, being 11-cis-retinal bound to a protein which is structurally similar to opsin. Colour selectivity is achieved by positioning specific amino acid side chains along the chromophore so as to perturb the absorption spectrum of the chromophore. 

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