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Optical properties of molecular beam epitaxially grown type II 'W' shaped GaSb/AlSb/InAs/GaIn(As)Sb/InAs/AlSb/GaSb quantum wells (QWs) designed for the active region of interband cascade lasers have been investigated. Temperature dependence of Fourier-transformed photoluminescence and photoreflectance was employed to probe the effects of addition of arsenic into the original ternary valence band well of GaInSb. It is revealed that adding arsenic provides an additional degree of freedom in terms of band alignment and strain tailoring and allows enhancing the oscillator strength of the active type II transition. On the other hand, however, arsenic incorporation apparently also affects the structural and optical material quality via generating carrier trapping states at the interfaces, which can deteriorate the radiative efficiency. These have been evidenced in several spectroscopic features and are also confirmed by cross-sectional transmission electron microscopy images. While arsenic incorporation into type II QWs is a powerful heterostructure engineering tool for optoelectronic devices, a compromise has to be found between ideal band structure properties and high quality morphological properties. [ABSTRACT FROM AUTHOR]

Background: Endothelial progenitor cells (EPCs) and cytokines seem to play a pivotal role in arterial healing after stent implantation. Using optical coherence tomography (OCT) as a high-resolution imaging technique, we aimed to assess the influence of circulating EPCs and levels of Il-1 cytokines on stent coverage and in-stent proliferation., Methods: Eighty-nine patients were randomly treated with either Xience V drug-eluting stent (DES; n = 48) or bare-metal stent (BMS) postdilated with the SeQuent Please drug-eluting balloon (DEB; n = 41). EPC populations (CD34+/CD133+ and CD34+/CD133+/KDR+ EPC) and cytokines (Il-1ra, Il-18, and Il-1α) were measured before percutaneous coronary intervention using flow cytometry or immunoassay. Vessel remodeling was analyzed using coronary angiography and OCT at 6-month follow-up., Results: Indexed neointimal volume and maximal proliferation thickness correlated inversely with EPC levels in the entire study population (r = -0.220; P=.04 and r = -0.253; P=.02) and the BMS + DEB subgroup (r = -0.344; P=.03 and r = -0.374; P=.02). Late lumen loss (LLL) was associated with the proatherogenic Il-18 concentration in the main population (r = 0.342; P=.01) and the BMS + DEB group (r = 0.471; P=.01). In the DES subgroup, associations with proliferation and LLL were lacking. Associations for stent strut coverage were not observed., Conclusions: A high EPC count seems to be a favorable individual patient factor, since it was associated with less instent proliferation. Contrarily, high Il-18 levels lead to more LLL, which emphasizes its proatherogenic properties.

Background: In this randomized trial, strut coverage and neointimal proliferation of a therapy of bare metal stents (BMSs) postdilated with the paclitaxel drug-eluting balloon (DEB) was compared with everolimus drug-eluting stents (DESs) at 6-month follow-up using optical coherence tomography. We hypothesized sufficient stent coverage at follow-up., Methods and Results: A total of 105 lesions in 90 patients were treated with either XIENCE V DES (n=51) or BMS postdilated with the SeQuent Please DEB (n=54). At follow-up, comparable results on the primary optical coherence tomography end point (percentage uncovered struts 5.64±9.65% in BMS+DEB versus 4.93±9.29% in DES; P=0.366) were found. Thus, BMS+DEB achieved the prespecified noninferiority margin of 5% uncovered struts versus DES (difference between treatment means, 0.71%; one-sided upper 95% confidence interval, 4.14%; noninferiority P=0.04). Optical coherence tomography analysis showed significantly more global neointimal proliferation in the BMS+DEB group (15.7±7.8 versus 11.0±5.2 mm(3) proliferation volume/cm stent length; P=0.002). No significant focal in-stent stenosis analyzed with angiography (percentage diameter stenosis at follow-up, 22.8±11.9 versus 16.9±10.4; P=0.014) and optical coherence tomography (peak local area stenosis, 39.5±13.8% versus 36.8±15.6%; P=0.409) was found., Conclusions: Good stent strut coverage of >94% was found in both therapy groups. Despite greater suppression of global neointimal growth in DES, both DES and BMS+DEB effectively prevented clinically relevant focal restenosis at 6-month follow-up., Clinical Trial Registration Url: http://www.clinicaltrials.gov. Unique identifier: NCT01056744., (© 2014 American Heart Association, Inc.)

Background: Safety concerns regarding use of drug-eluting stent systems (DES) are related mostly to late stent thrombosis, which is facilitated by incomplete stent endothelial coverage. Specific information about time course and amount of endothelial strut coverage of different DES is required, in order to further refine the concept of antiplatelet therapy after DES implantation. Optical coherence tomography (OCT) is emerging as a new gold standard for endovascular imaging of stents, atherosclerosis progression, vulnerable plaque, and neointimal proliferation. The aim of this study is a comparative evaluation using OCT of the XIENCE V everolimus-eluting stent (Abbot Vascular, Santa Clara, CA, USA) on one hand, and the bare metal stent Coroflex Blue postdilated with the paclitaxel-eluting balloon Sequent Please (both from B Braun Melsungen AG, Melsungen, Germany) on the other hand, with respect to endothelial coverage and neointimal proliferation., Methods: Eighty patients scheduled for elective percutaneous coronary intervention (PCI) of a native coronary stenosis suitable for DES implantation and OCT imaging are scheduled to be openly randomised 1:1 to either XIENCE or Coroflex Blue/Sequent Please. The study is conducted prospectively at a university high-volume PCI centre with OCT expertise. Angiographic follow-up and time-domain OCT imaging with motorised pull-back at 1 mm/s are planned six months after study stent implantation in all patients. OCT endpoints are: (1) endothelial coverage, expressed as % of struts without coverage and % of stent length containing non-covered struts, and respectively (2) neointimal proliferation, given as % neointimal volumetric proliferation within the whole stent and also as peak focal % neointimal area proliferation. The study is not powered for clinical endpoints, which are: subacute or late stent thrombosis and need for revascularisation of the stent segment. Given the high number of measurements (15 cross-section images / 1 mm stent length), OCT endpoints are likely to reach significance at the level p <0.05, if the drop-out rate in follow-up does not exceed 20%., Current Status: The study is currently on-going and its termination is scheduled for February 2010. (ClinicalTrials.gov identifier: NCT01056744).

Protein-RNA and protein-protein interactions involved in the assembly of the signal recognition particle (SRP) were examined using fluorescence spectroscopy. Fluorescein was covalently attached to the 3'-terminal ribose of SRP RNA following periodate oxidation, and the resulting SRP RNA-Fl was reconstituted into a fluorescent SRP species that was functional in promoting translocation of secretory proteins across the membrane of the endoplasmic reticulum. Each of the two protein heterodimers purified from SRP elicited a substantial change in fluorescein emission upon association with the modified RNA. The binding of SRP9/14 to singly-labeled SRP RNA-Fl increased fluorescein emission intensity by 41% at pH 7.5 and decreased its anisotropy from 0.18 to 0.16. The binding of SRP68/72 increased the fluorescein anisotropy from 0.18 to 0.23 but did not alter the emission intensity of SRP RNA-Fl. These fluorescence changes did not result from a direct interaction between the dye and protein because the fluorescein remained accessible to both iodide ions and fluorescein-specific antibodies in the complexes. The spectral changes were elicited by specific SRP RNA-protein interactions, since (i) the SRP9/14- and SRP68/72-dependent changes were unique, (ii) an excess of unlabeled SRP RNA, but not of tRNA, blocked the fluorescence changes, and (iii) no emission changes were observed when SRP RNA-Fl was titrated with other RNA-binding proteins. Each heterodimer bound tightly to the RNA, since the Kd values determined spectroscopically and at equilibrium for the SRP9/14 and the SRP68/72 complexes with SRP RNA-Fl were less than 0.1 and 7 +/- 3 nM, respectively. The binding affinity of SRP68/72 for SRP RNA-Fl was unaffected by the presence of SRP9/14, and hence the binding of the heterodimers to SRP RNA is noncooperative in the absence of SRP54 and SRP19. The SRP protein heterodimers therefore associate randomly and independently with SRP RNA to form domains in the particle that are distinct both structurally and functionally. Any cooperativity in SRP assembly would have to be mediated by SRP54 and/or SRP19.

The ubiquity of elongation factor Tu (EF-Tu)-dependent conformational changes in amino-acyl-tRNA (aa-tRNA) and the origin of the binding energy associated with aa-tRNA.EF-Tu.GTP ternary complex formation have been examined spectroscopically. Fluorescein was attached covalently to the 4-thiouridine base at position 8 (s4U-8) in each of four elongator tRNAs (Ala, Met-m, Phe, and Val). Although the probes were chemically identical, their emission intensities in the free aa-tRNAs differed by nearly 3-fold, indicating that the dyes were in different environments and hence that the aa-tRNAs had different tertiary structures near s4U-8. Upon association with EF-Tu.GTP, the emission intensities increased by 244%, 57%, or 15% for three aa-tRNAs due to a change in tRNA conformation; the fourth aa-tRNA exhibited no fluorescence change upon binding to EF-Tu.GTP. Despite the great differences in the emission intensities of the free aa-tRNAs and in the magnitudes of their EF-Tu-dependent intensity increases, the emission intensity per aa-tRNA molecule was nearly the same (within 9% of the average) for the four aa-tRNAs when bound to EF-Tu-GTP. Thus, the binding of EF-Tu.GTP induced or selected a tRNA conformation near s4U-8 that was very similar, and possibly the same, for each aa-tRNA species. It therefore appears that EF-Tu functions, at least in part, by minimizing the conformational diversity in aa-tRNAs prior to their beginning the recognition and binding process at the single decoding site on the ribosome. Since an EF-Tu-dependent fluorescence change was also observed with fluorescein-labeled tRNA(Phe), the protein-dependent structural change is effected by direct interactions between EF-Tu and the tRNA and does not require the aminoacyl group. The Kd of the tRNA(Phe).EF-Tu.GTP ternary complex was determined, at equilibrium, to be 2.6 microM by the ability of the unacylated tRNA to compete with fluorescent Phe-tRNA for binding to the protein. Comparison of this Kd with that of the Phe-tRNA ternary complex showed that in this case the aminoacyl moiety contributed 4.3 kcal/mol toward ternary complex formation at 6 degrees C but that the bulk of the binding energy in the ternary complex was derived from direct protein-tRNA interactions.(ABSTRACT TRUNCATED AT 400 WORDS)