Modulation effects

More sophisticated pulse sequences have been developed to detect nuclear modulation effects. With a five-pulse sequence it is theoretically possible to obtain modulation amplitudes up to eight times greater than in a tlnee-pulse experunent, while at the same time the umnodulated component of the echo is kept close to zero. A four-pulse ESEEM experiment has been devised to greatly improve the resolution of sum-peak spectra. 

A simulation performed using a potential of mean force enables the modulating effects of t solvent to be taken into account. The solvent also influences the dynamic beliaviour of t... 

CarbocycHc 2/3 -didehydro-2/3 -dideoxyguanosine [118353-05-2] (carbovk, CBV, 66), C H 2N502, synthesized in 1988 (177), is a promising candidate for the chemotherapy of AIDS. CBV inhibits HIV repHcation and HIV-induced cytopathic effects in a variety of human T-lymphoblastoid ceU lines at concentrations approximately two hundred- to four hundredfold below its cytotoxic concentrations (177). CBV is as effective as AZT and DDC in reducing the expression of vkal antigen in HIV-infected CEM ceUs (177). The antivkal potency and selectivity of carbovk is comparable to the anti-HIV-1 potency and selectivity of 2/3 -dideoxyadenosine (178). The exact mode of antivkal action of carbovk has not yet been elucidated, but may be the modulating effect of intraceUular nucleotides on 5 -nucleotidase activity (179). 

Several recent expert reviews and workshops have discussed the effects of endocrine disruption on wildlife and especially invertebrate species. These include the EU workshop on the impact of endocrine disrupters on human health and wildlife (Weybridge, 1996), the lEH workshop (Leicester, May 1997), the Environment Agency Consultative report (January 1998) and the Tyndall Forum at the Royal Institution (February 1998). They have concluded that endocrine disruption may have far-reaching adverse consequences for biodiversity and the sustainability of natural ecosystems. More comprehensive bioassay systems are required to identify and assess chemicals alleged to produce endocrine modulating effects. 

However, as follows from the results presented in Fig. 1(b), the behavior of the PMF for the case of adsorbed dispersion in the matrix at Pm< m — 0.386 contains interesting features in addition to those shown in Fig. 1(a). We observe that the PMF is modulated by the presence of solvent species and in addition is modulated by the presence of matrix particles. The structural repulsive barrier appears, due to matrix particles. An additional weak attractive minimum exists at separations corresponding to matrix-separated colloids. It is interesting that the effects of solvent modulation of the PMF in the adsorbed dispersion are seen for matrix separated colloids. The matrix particles are larger than colloids adsorption of solvent species on the surface of a matrix particle is stronger than on the surface of a colloid. Therefore, the solvent modulating effects of the PMF result from colloids separated by a matrix particle covered by a single layer of solvent species. 

Figure 5.19 Modulation effects of a doublet and triplet by a spin-echo pulse sequence, 90°-T-180°-T-echo.

Hyperfine coupling constants provide a direct experimental measure of the distribution of unpaired spin density in paramagnetic molecules and can serve as a critical benchmark for electronic wave functions [1,2], Conversely, given an accurate theoretical model, one can obtain considerable information on the equilibrium stmcture of a free radical from the computed hyperfine coupling constants and from their dependenee on temperature. In this scenario, proper account of vibrational modulation effects is not less important than the use of a high quality electronic wave function. 

Mortensen A, Ladefoged O. 1992. Delayed neurotoxicity of trixylenyl phosphate and a trialkyl/aryl phosphate mixture, and the modulating effect of atropine on tn-ortho-to y phosphate-induced neurotoxicity. NeuroToxicology 13 347-354. 

Figure 1 schematically shows the modulation effects on galactic and solar particles and their interactions. 

Zhou W, Koldzic-Zivanovic N, Clarke CH, de Beun R, Wassermann K, Bury PS, Cunningham KA, Thomas ML (2002) Selective estrogen receptor modulator effects in the rat brain. Neuroendocrinology 75 24-33... 

At higher NO concentrations, MPO activity is inhibited through formation of an inactive ferric nitrosyl complex MPO(NO) the rate constant kori is 1.07xlO6 M-1s-1 and the dissociation rate constant, kQff, is 10.8 s-1 (pH 7.0 phosphate buffer at 10 °C) (Scheme 9, pathway A). However, the inhibitory effects of NO are reduced in the presence of plasma levels of Cl- (100 mM) where on and kQ rate constants were determined to be 1.5 x 105 M-1s-1 and 22.8 s-1, respectively. The modulating effects of NO on MPO activity parallel that of O2 which accelerates activity by serving as a substrate for compound II and inhibits activity by acting as a ligand for MPO (Scheme 9, pathway B) (29). 

ESE envelope modulation. In the context of the present paper the nuclear modulation effect in ESE is of particular interest110, mi. Rowan et al.1 1) have shown that the amplitude of the two- and three-pulse echoes1081 does not always decay smoothly as a function of the pulse time interval r. Instead, an oscillation in the envelope of the echo associated with the hf frequencies of nuclei near the unpaired electron is observed. In systems with a large number of interacting nuclei the analysis of this modulated envelope by computer simulation has proved to be difficult in the time domain. However, it has been shown by Mims1121 that the Fourier transform of the modulation data of a three-pulse echo into the frequency domain yields a spectrum similar to that of an ENDOR spectrum. Merks and de Beer1131 have demonstrated that the display in the frequency domain has many advantages over the parameter estimation procedure in the time domain. 

Morris, M.E. and Pang, K.S. (1987) Competition between two enzymes for substrate removal in liver modulating effects due to substrate recruitment of hepatocyte activity. Journal of Pharmacokinetics and Biopharmaceutics, 15, 473-496. 

Lo Y-L (2003) Relationships between the hydrophilic-lipophilic balance values of pharmaceutical excipients and their multidrug resistance modulating effect in Caco-2 cells and rat intestines. J Control Release 90 37 -8... 

While the distinct amino acid residues have mostly only a modulating effect (see Table 1.9) (e.g., FMOC-protected amino acids), the type of protection group or derivative formed decides on the molecular and chiral recognition mechanism and hence on the obtained elution order as well as the level of enantiomer recognition (i.e., magnitudes of a-values) that can be afforded. From a practical point of view, we may distinguish between two groups of IV-derivatives ... 

Liang KC, Juler RG, McGaugh JL. 1986. Modulating effects of posttraining epinephrine on memory involvement of the amygdala noradrenergic system. Brain Res 368(1) 125-133. 

Abreu-Villaca Y, Seidler FJ, et al (2004) Does prenatal nicotine exposure sensitize the brain to nicotine-induced neurotoxicity in adolescence Neuropsychopharmacology 29(8) 1440-1450 Acri JB (1994) Nicotine modulates effects of stress on acoustic startle reflexes in rats dependence on dose, stressor and initial reactivity. Psychopharmacology 116(3) 255-265... 

Guyonnet D, Berges R, Siess MH, Pinnert ME, Chagnon MC, Suschetet M, Le Bon AM. (2004) Post-initiation modulating effects of allyl sulfides in rat hepatocarcinogenesis. Food Chem Toxicol 42 1479-1485. 

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