Perturbation difference

G3 f eq ID files select, perturbed, different target spins... 

Sogami, M. and Ogura, S. 1973. Structural transition in bovine plasma albumin. Location of tyrosyl and tryptophyl residues by solvent perturbation difference spectra. 

In solution, rotational fine structures are not observed because molecular collisions (10 13s) occur before one rotation is completed (10 "s) and the levels of individual molecules are perturbed differently. In the solid state, molecular rotation does not occur because of intermo-lecular interactions. 

Extension of pseudopotential theory to the transition metals preceded the use of the Orbital Correction Method discussed in Appendix E, but transition-metal pseudopotentials are a special case of it. In this method, the stales are expanded as a linear combination of plane waves (or OPW s) plus a linear combination of atomic d states. If the potential in the metal were the same as in the atom, the atomic d states would be eigenstates in the metal and there would be no matrix elements of the Hamiltonian with other slates. However, the potential ix different by an amount we might write F(r), and there arc, correspondingly, matrix elements (k 1 // 1 r/> = hybridizing the d states with the frce-eleclron states. The full analysis (Harrison, 1969) shows that the correct perturbation differs from (5K by a constant. The hybridization potential is... 

Conventional UV difference spectroscopy and solvent perturbation difference spectroscopy have been used in a wide variety of protein stud-... 

All of the a-lactalbumins and lysozymes studied, except the egg lysozymes, have negative bands near 270 nm. It is not possible to allocate these bands unequivocally, but they appear to involve Tyr perturbation. Differences in chirality of the disulfide bridges in a-lactalbumin and lysozyme may also cause appreciable contribution to bands in the 240- to 270-nm region. 

HSQC or HSQC-TOCSY Difference Spectra In cases where there is an obvious control sample and one with some perturbation, difference spectra can be... 

Drescher, K., G. Cornelius L. Reusing. 1982. Phase response curves obtained by perturbing different variables of a 24 hr model oscillator based on translational control. J. Theor. Biol. 94 345-53. 

Vibrational spectra are accompanied by rotational transitions. Rgure 1-4 shows the rotational fine structure observed for the gaseous ammonia molecule. In most polyatomic molecules, however, such a rotational fine structure is not observed because the rotational levels are closely spaced as a result of relatively large moments of inertia. Vibrational spectra obtained in solution do not exhibit rotational fine structure, since molecular collisions occur before a rotation is completed and the levels of the individual molecules are perturbed differently. Since Raman spectra are often obtained in liquid state, they do not exhibit rotational fine structure. 

Figure 1.18. Perturbation difference spectra of amino acids produced by 20% (v/v) ethlyene glycol. Source Donovan, W., 1969, J. Biol. Cliem. 244,1961-1967 Authorizatbn of reprint accorded by the Biochemical Society for Biochemistry and Molecular Biology.

Up to now we have dealt with the sensitivity analysis of theoretical perturbations (dN,dv). The question arises to what extent these are related to real physical perturbations and whether the ehanges in the electron density distribution correlate with the ones predicted by the sensitivity coefficients. Real perturbations differ from theoretical ones in that they arc not infinitesimal and, for dv, that they are not restricted to one single atom in the molecule. 

Figure 1. Dependence of specific rotation at 313 nm on pH value, BSA in 0.02 M thiocyanate. Distribution of N and F components as determined by electrophoresis shown in upper dashed line, results of perturbation difference spectra in lower broken line. From Leonard and Foster (1%1).

The interference of water absorption is eliminated when the physicochemical and dynamic approaches are used for measuring the spectra, since a water response to a perturbation differs from that of a protein (vide supra). As an alternative, the spectrum can be rendered practically free from background absorption with a polarization modulation technique. To illustrate. Fig. 7.54 shows the spectrum from PM-IRRAS of an acetylcholinesterase (AChE) (enzyme) monolayer at the air-water interface at different surface pressures [838]. The spectra were... 

The barriers to rotation of the C-N and C-0 bonds in (33) and (34) were calculated from n.m.r. spectral data the i a values obtained were ca. 76 4 and 50 3 kj mol respectively, in CDCla. Complexation of MejAu with nucleotides was investigated by Raman perturbation difference spectroscopy. ... 

Fig. 6.1. Perturbation difference spectra of several amino acids produced by 20% (vol/vol) ethylene glycol (A) tyrosine, (B) tryptophan, (C) cystine, (D) histidine, and (E) phenylalanine (courtesy of Donovan, 1969a).

Bello, J. Thermal Perturbation Difference Spectra of Proteins Containing Tryp-tophyl Residues. Biochemistry 9, 3562-3568 (1970). 

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