Optically stimulated electron paramagnetic resonance: Simplicity, versatility, information content.

A simple technique for observing optically stimulated electron paramagnetic resonance (OSEPR) is proposed and investigated. The versatility and information content of the described technique is demonstrated by the example of the OSEPR spectra of systems that are unpopular for this type of spectroscopy: a crystal with rare-earth ions Nd3+ and a doped semiconductor GaAs. In addition, the OSEPR spectrum of atomic cesium is presented, in which an optical nonlinearity is observed that makes it possible to estimate the Rabi frequency for the relevant optical transition. The effects observed in the described experiments (switching of peaks to dips, light-induced splitting of the OSEPR lines, and the appearance of a spectral feature at the double-Larmor frequency) are interpreted using the model proposed in the theoretical part of the work. The suggested interpretation shows the possibility of using the described OSEPR technique to estimate not only 'magnetic' parameters of the model Hamiltonian (g-factors, spin relaxation times), but also the Rabi frequencies characterizing optical transitions.

Spin Noise in Birefringent Media.

It is known that linear birefringence of the medium essentially hinders measuring the Faraday effect. For this reason, optically anisotropic materials have never been considered as objects of the Faraday-rotation-based spin noise spectroscopy. We show, both theoretically and experimentally, that strong optical anisotropy that may badly suppress the regular Faraday rotation of the medium, practically does not affect the measurement of the spatially uncorrelated spin fluctuations. We also show that the birefringent media provide additional opportunity to measure spatial spin correlations. Results of the experimental measurements of the spin-noise spectra performed on Nd^{3+} ions in the uniaxial crystal matrices well agree with the theory.

Raman scattering model of the spin noise.

The mechanism of formation of the polarimetric signal observed in the spin noise spectroscopy (SNS) is analyzed from the viewpoint of the light scattering theory. A rigorous calculation of the polarimetric signal (Faraday rotation or ellipticity) recorded in the SNS is presented in the approximation of single scattering. We show that it is most correctly to consider this noise as a result of scattering of the probe light beam by fluctuating susceptibility of the medium. Fluctuations of the gyrotropic (antisymmetric) part of the susceptibility tensor lead to appearance of the typical for the SNS Faraday rotation noise at the Larmor frequency. At the same time, fluctuations of linear anisotropy of the medium (symmetric part of the susceptibility tensor) give rise to the ellipticity noise of the probe beam spectrally localized at the double Larmor frequency. The results of the theoretical analysis well agree with the experimental data on the ellipticity noise in cesium vapor.

Heterodyne detection of scattered light: application to mapping and tomography of optically inhomogeneous media.

The signal registered by a plane photodetector placed behind an optically inhomogeneous object irradiated by two coherent Gaussian beams intersecting inside the object at a small angle to each other is calculated in the single-scattering approximation. In the considered arrangement, only one of the beams hits the detector and serves as the local oscillator for heterodyning the field scattered by the other beam (not hitting the detector). The results of analytical calculation show that the signal detected in this way is contributed only by the region of the inhomogeneous object where the two beams overlap. By moving the scatterer with respect to the overlap region and monitoring the heterodyned signal, with the aid of the derived expression, one can reconstruct the refractive-index relief of the scatterer. We also propose a simple method of spatial mapping of the sample that allows one to estimate the magnitude and characteristic dimensions of the inhomogeneities.

Optical spectroscopy of spin noise.

Spontaneous fluctuations of the magnetization of a spin system in thermodynamic equilibrium (spin noise) manifest themselves as noise in the Faraday rotation of probe light. We show that the correlation properties of this noise over the optical spectrum can provide clear information about the composition of the spin system that is largely inaccessible for conventional linear optics. Such optical spectroscopy of spin noise, e.g., allows us to clearly distinguish between optical transitions associated with different spin subsystems, to resolve optical transitions that are unresolvable in the usual optical spectra, to unambiguously distinguish between homogeneously and inhomogeneously broadened optical bands, and to evaluate the degree of inhomogeneous broadening. These new possibilities are illustrated by theoretical calculations and by experiments on paramagnets with different degrees of inhomogeneous broadening of optical transitions [atomic vapors of 41K and singly charged (In,Ga)As quantum dots].

[Long-term follow-up use of "cypher" sirolimus-eluting stents in patients with coronary heart disease after coronary artery bypass grafting with occlusive lesions of the coronary artery].

UNLABELLED: The aim of this study is to assess the 1 and 2-year follow-up of treatment with Cypher drug- eluting stents (Cordis, Johnson & Johnson, USA) for chronic symptomatic coronary artery occlusions in CHD patients after coronary artery bypass graft. That was a retrospective study that included 51 patients who had been implanted Cypher stents. A control group comprised 65 symptomatic patients with coronary heart disease (CHD) after coronary artery bypass grafting with occlusive lesions of the coronary artery, who was carried out only conservative treatment (without PTCA). Patients received standard medicamentous treatment. The groups did not differ in clinical characteristics. 79 stenoses in the eluting stent groups were subject to revascularization. The immediate cure rate was 84.3%. During the follow-up, one patient (2.3%) died and 4 (9.3%) underwent coronary bypass surgery in the drug- eluting stent group; there were 3 (4.6%) deaths and 10 (15.4%) patients had coronary bypass surgery in the control group. After stenting we noted a reliable decrease of patients with anginal attacks, of the used nitrates, increase the average physical tolerance by stress- testing (p < 0.05) than by patients in control group. CONCLUSION: stenting chronic coronary artery occlusions in patients with coronary heart disease (CHD) after coronary artery bypass grafting with the use of Cypher drug- eluting stents (Cordis, Johnson & Johnson, USA) is an effective procedure from the viewpoint of long-term results, with low frequency of recurrent angina and repeated myocardial revascularization.

[The main principles of the organization of modern fighting injury radiation diagnosis in a diversified in-patient department].

On the base of accumulated experience in the main principles of the organization of modern fighting injury radiation diagnosis authors propose usage of the most informatory for the injured method of radiation diagnosis on the first stage of the examination. In a specialized diversified hospital the examination of the injured should begin with computed tomography enabling to obtain maximum information in minimum time about injures got, which is most important for the reduction of the preoperational period.

ERp57 and PDI: multifunctional protein disulfide isomerases with similar domain architectures but differing substrate-partner associations.

Secretory proteins become folded and acquire stabilizing disulfide bonds in the endoplasmic reticulum (ER). Correct disulfide bond formation is a key step in ER quality control (ERQC). Proteins with incorrect disulfide bonds are recognized by the quality control machinery and are retrotranslocated into the cytosol where they are degraded by the proteasome. The mammalian ER contains 17 disulfide isomerases and at least one of them, ERp57, works in conjunction with the ER lectin-like chaperones calnexin and calreticulin. The targeting of ERp57 to calnexin-calreticulin is mediated by its noncatalytic b' domain, and analogous domains in other disulfide isomerases likely determine their substrate and partner preferences. This review discusses some explanations for the multiplicity of disulfide isomerases and highlights structural differences in the b' domains of PDI and ERp57 as an example of how noncatalytic domains define specialized roles in oxidative folding.

Oral testosterone undecanoate reverses erectile dysfunction associated with diabetes mellitus in patients failing on sildenafil citrate therapy alone.

AIMS: To evaluate the cause of failure of sildenafil citrate (Viagra) to restore erections in patients with organic erectile dysfunction (ED) associated with type II diabetes mellitus (DM) and receiving oral antidiabetic drugs. METHODS: Diabetic ED patients (n = 120), aged 43-74 years, failing to respond at least three times to 100 mg Viagra were evaluated. After at least 2 weeks' treatment with oral testosterone undecanoate (Andriol), 100 mg Viagra was used before coitus. ED was assessed with the International Index of Erectile Function (IIEF). Serum total testosterone, prolactin, thyroid stimulating hormone, lipid profile and prostate-specific antigen (PSA) were determined by standard methods and prostate volume by digital rectal examination. Age-matched diabetic ED patients (n = 100) served as controls for baseline values. RESULTS: Viagra non-responders had, at baseline, significantly lower testosterone and more depressed libido than controls. Andriol restored testosterone to normal levels and increased libido. In 84/120 (70%) Viagra non-responders, combined therapy with Andriol induced satisfactory erections, a significant increase in IIEF scale (question (Q) 3 from 2.0 +/- 0.2 to 3.7 +/- 0.3, Q4 from 1.9 +/- 0.1 to 3.4 +/- 0.2, Q12 from 1.0 +/- 0.1 to 4.2 +/- 0.4) and increased sexual contacts from 0.5 to 3-4 per month. No adverse events were noted, and PSA levels remained below 4 ng/ml. CONCLUSION: Decreased testosterone levels in patients with ED and type II DM receiving oral antidiabetic against may be responsible for failure to respond to sildenafil citrate therapy. Combination with oral testosterone undecanoate restores sexual function in these patients.

[Endovascular embolization of arteriosinusoidal fistula with new coil type]. / Endovaskuliarnaia émbolizatsiia arterio-sinusnogo soust'ia novym tipom spiralei.

A case report for endovascular embolization of cerebral arteriosinusoidal fistula with new coil type is presented. Endovascular procedure enabled to avoid extensive surgical intervention and provided the evidence of its effectiveness for management of patients with cerebral arteriovenous malformations.

[A quick method for estimation of fractal dimensions of macromolecular coils of biopolymers in solutions]. / Ekspress-metod otsenki fraktal'noi razmernosti makromolekuliarnykh klubkov biopolimerov v rastvore.

The viscometric measurements were used to assess the fractal dimensions of macromolecular coils in solutions. The relationships between the fractal dimensions and other hydrodynamic properties were determined. These data were used to determine the parameters of the Mark-Houwink equation.

Structure and function of the C-terminal PABC domain of human poly(A)-binding protein.

We have determined the solution structure of the C-terminal quarter of human poly(A)-binding protein (hPABP). The protein fragment contains a protein domain, PABC [for poly(A)-binding protein C-terminal domain], which is also found associated with the HECT family of ubiquitin ligases. By using peptides derived from PABP interacting protein (Paip) 1, Paip2, and eRF3, we show that PABC functions as a peptide binding domain. We use chemical shift perturbation analysis to identify the peptide binding site in PABC and the major elements involved in peptide recognition. From comparative sequence analysis of PABC-binding peptides, we formulate a preliminary PABC consensus sequence and identify human ataxin-2, the protein responsible for type 2 spinocerebellar ataxia (SCA2), as a potential PABC ligand.

Correlation analysis of spectral fluctuations in inhomogeneously broadened spectra.

It is shown that the lineshapes of inhomogeneously broadened spectra, due to the statistical nature of their formation, exhibit spectral fluctuations. Formulas are obtained that allow one, based on correlation analysis of different realizations of the inhomogeneously broadened line, to reconstruct its homogeneous lineshape and to evaluate the number of centers involved in its formation. The magnitude of these spectral fluctuations is estimated and it is shown that the proposed method can be efficiently used in practice.

Structural proteomics of an archaeon.

A set of 424 nonmembrane proteins from Methanobacterium thermoautotrophicum were cloned, expressed and purified for structural studies. Of these, approximately 20% were found to be suitable candidates for X-ray crystallographic or NMR spectroscopic analysis without further optimization of conditions, providing an estimate of the number of the most accessible structural targets in the proteome. A retrospective analysis of the experimental behavior of these proteins suggested some simple relations between sequence and solubility, implying that data bases of protein properties will be useful in optimizing high throughput strategies. Of the first 10 structures determined, several provided clues to biochemical functions that were not detectable from sequence analysis, and in many cases these putative functions could be readily confirmed by biochemical methods. This demonstrates that structural proteomics is feasible and can play a central role in functional genomics.

Rapid fold and structure determination of the archaeal translation elongation factor 1beta from Methanobacterium thermoautotrophicum.

The tertiary fold of the elongation factor, aEF-1beta, from Methanobacterium thermoautotrophicum was determined in a high-throughput fashion using a minimal set of NMR experiments. NMR secondary structure prediction, deuterium exchange experiments and the analysis of chemical shift perturbations were combined to identify the protein fold as an alpha-beta sandwich typical of many RNA binding proteins including EF-G. Following resolution of the tertiary fold, a high resolution structure of aEF-1beta was determined using heteronuclear and homonuclear NMR experiments and a semi-automated NOESY assignment strategy. Analysis of the aEF-1beta structure revealed close similarity to its human analogue, eEF-1beta. In agreement with studies on EF-Ts and human EF-1beta, a functional mechanism for nucleotide exchange is proposed wherein Phe46 on an exposed loop acts as a lever to eject GDP from the associated elongation factor G-protein, aEF-1alpha. aEF-1beta was also found to bind calcium in the groove between helix alpha2 and strand beta4. This novel feature was not observed previously and may serve a structural function related to protein stability or may play a functional role in archaeal protein translation.

Solution structure of the PDZ2 domain from human phosphatase hPTP1E and its interactions with C-terminal peptides from the Fas receptor.

The solution structure of the second PDZ domain (PDZ2) from human phosphatase hPTP1E has been determined using 2D and 3D heteronuclear NMR experiments. The binding of peptides derived from the C-terminus of the Fas receptor to PDZ2 was studied via changes in backbone peptide and protein resonances. The structure is based on a total of 1387 nonredundant experimental NMR restraints including 1261 interproton distance restraints, 45 backbone hydrogen bonds, and 81 torsion angle restraints. Analysis of 30 lowest-energy structures resulted in rmsd values of 0.41 +/- 0.09 A for backbone atoms (N, Calpha, C') and 1.08 +/- 0.10 A for all heavy atoms, excluding the disordered N- and C-termini. The hPTP1E PDZ2 structure is similar to known PDZ domain structures but contains two unique structural features. In the peptide binding domain, the first glycine of the GLGF motif is replaced by a serine. This serine appears to replace a bound water observed in PDZ crystal structures that hydrogen bonds to the bound peptide's C-terminus. The hPTP1E PDZ2 structure also contains an unusually large loop following strand beta2 and proximal to the peptide binding site. This well-ordered loop folds back against the PDZ domain and contains several residues that undergo large amide chemical shift changes upon peptide binding. Direct observation of peptide resonances demonstrates that as many as six Fas peptide residues interact with the PDZ2 domain.