Terahertz Selective Emission Enhancement from a Metasurface-Coupled Photoconductive Emitter in Quasi-Near-Field Zone

We present a THz emission enhancement of 41 times at 0.92 THz from a metasurface made of T-shaped resonators excited in a quasi-near-field zone. Such a metasurface has an intrinsic transmission minimum with Q factor of 4 at 1.25 THz under far-field excitation. When this metasurface is coupled onto the backside of a 625-μm-thick photoconductive emitter, the metasurface is below the Fraunhofer distance to the excitation source. As such, one broad enhancement around 0.47 THz and another extremely narrow enhancement at 0.92 THz in the emission spectrum are observed owing to a quasi-near-field excitation. Theoretically, the Q factor of the latter is up to 307, which is limited by the spectral resolution in experiment. The numerical simulations indicate that the T-shaped resonators serve as an array of plasmonic antennas resulting in the aforementioned emission enhancement of THz radiation.

     

Spermine as a possible endogenous allosteric activator of carboxypeptidase A: multispectroscopic and molecular simulation studies

Abstract

Carboxypeptidase A (EC.3.4.17.1) is a zinc-containing proteolytic enzyme that removes the C-terminal amino acid from a peptide chain with the free carboxylate-terminal. In this study, the effect of spermine interaction on the structure and thermal stability of Carboxypeptidase A was investigated by ultraviolet???visible spectroscopy, fluorescence spectroscopy, circular dichroism, Kinetic measurement, molecular docking and simulation studies have also been followed at the pH of 7.5. The transition temperature of Carboxypeptidase A, as a criterion of protein thermal stability, in the presence of spermine was enhanced by increasing the concentration of spermine. The results of fluorescence intensity changes, at two temperatures of 308 and 318?K, also suggested that spermine had a great ability to quench the fluorescence of Carboxypeptidase A through the static quenching procedure. The thermodynamic parameters changes, including standard Gibbs free-energy, entropy and enthalpy, showed that the binding of spermine to Carboxypeptidase A was spontaneous and the hydrogen bonding and van der Waals interactions played a major role in stabilizing the Carboxypeptidase A–spermine complex. The changes in the content of the α-helix and the β-sheet of the Carboxypeptidase A with binding to spermine were shown by the CD spectra method. Further, kinetic studies revealed that by increasing concentration of spermine, the activity of Carboxypeptidase A was enhanced. Also, the docking study revealed that the hydrogen bonding and van der Waals interactions played a major role in stabilizing the Carboxypeptidase A–spermine complex. As a result, spermine could be considered as an activator and a stabilizer for Carboxypeptidase A.

Communicated by Ramaswamy H. Sarma     

Formation and stabilization of five-coordinate iron(II) verdoheme analogues by axial weakly coordinating anion ligation. X-ray crystal structures of [(OEOPFe)2O](X)2 (X = AsF6, SbF6)

The effect of weakly coordinating anions, , as axial ligands on the formation and coordination chemistry of verdoheme analogues have been examined. Two new five-coordinate and stable iron(II) verdoheme analogues, [OEOPFe^IIX], where OEOP is the monoanion of octaethyloxoporphyrin and X = AsF₆ and SbF₆, have been isolated. The compounds have been characterized by different spectroscopic methods as well as elemental analysis. ¹H NMR spectroscopy and magnetic moment measurements show that the [OEOPFe^IIX] are paramagnetic and iron is five-coordinate. Exposure of dichloromethane solutions of [OEOPFe^IIX] (X = AsF₆ (2), SbF₆ (3)) to dioxygen result in their transformation into the μ-oxo bridged compounds, [(OEOPFe)₂O](X)₂ (X = AsF₆ (4), SbF₆ (5)). The structures of 4 and 5 have been determined by X-ray diffraction analysis, both are structurally similar with a P2₁/c space group in the monoclinic crystal system.     

Fetal programming: testosterone exposure of the female sheep during midgestation disrupts the dynamics of its adult gonadotropin secretion during the periovulatory period

Prenatal exposure of the female sheep to excess testosterone (T) leads to hypergonadotropism, multifollicular ovaries, and progressive loss of reproductive cycles. We have determined that prenatal T treatment delays the latency of the estradiol (E2)-induced LH surge. To extend this finding into a natural physiological context, the present study was conducted to determine if the malprogrammed surge mechanism alters the reproductive cycle. Specifically, we wished to determine if prenatal T treatment 1) delays the onset of the preovulatory gonadotropin surge during the natural follicular phase rise in E2, 2) alters pulsatile LH secretion and the dynamics of the secondary FSH surge, and 3) compromises the ensuing luteal function. Females prenatally T-treated from Day 60 to Day 90 of gestation (147 days is term) and control females were studied when they were approximately 2.5 yr of age. Reproductive cycles of control and prenatally T-treated females were synchronized with PGF2alpha, and peripheral blood samples were collected every 2 h for 120 h to characterize cyclic changes in E2, LH, and FSH and then daily for 14 days to monitor changes in luteal progesterone. To assess LH pulse patterns, blood samples were also collected frequently (each 5 min for 6 h) during the follicular and luteal phases of the cycle. The results revealed that, in prenatally T-treated females, 1) the preovulatory increase in E2 was normal; 2) the latencies between the preovulatory increase in E2 and the peaks of the primary LH and FSH surges were longer, but the magnitudes similar; 3) follicular-phase LH pulse frequency was increased; 4) the interval between the primary and secondary FSH surges was reduced but there was a tendency for an increase in duration of the secondary FSH surge; but 5) luteal progesterone patterns were in general unaltered. Thus, exposure of the female to excess T before birth produces perturbances and maltiming in periovulatory gonadotropin secretory dynamics, but these do not produce apparent defects in cycle regularity or luteal function. To reveal the pathologies that lead to the eventual subfertility arising from excess T exposure during midgestation, studies at older ages must be conducted to assess if there is progressive disruption of neuroendocrine and ovarian function.     

Lactobacillus gasseri in the Upper Small Intestine Impacts an ACSL3-Dependent Fatty Acid-Sensing Pathway Regulating Whole-Body Glucose Homeostasis

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Association of admission testosterone level with ST-segment resolution in male patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention

Background

Low level of testosterone may be associated with cardiovascular diseases in men, as some evidence suggests a protective role for testosterone in cardiovascular system. Little is known about the possible role of serum testosterone in response to reperfusion therapy in ST-elevation myocardial infarction (STEMI) and its relationship with ST-segment recovery. The present study was conducted to evaluate the association of serum testosterone levels with ST-segment resolution following primary percutaneous coronary intervention (PPCI) in male patients with acute STEMI.

Methods

Forty-eight men (mean age 54.55 ± 12.20) with STEMI undergoing PPCI were enrolled prospectively. Single-lead ST segment resolution in the lead with maximum baseline ST-elevation was measured and patients were divided into two groups according to the degree of ST-segment resolution: complete (> or =50%) or incomplete (<50%). The basic and demographic data of all patients, their left ventricular ejection fraction (LVEF) and laboratory findings including serum levels of free testosterone and cardiac enzymes were recorded along with angiographic finding and baseline TIMI (Thrombolysis in Myocardial Infarction) flow and also in-hospital complications and then these variables were compared between two groups.

Results

A complete ST-resolution (≥50%) was observed in 72.9% of the patients. The serum levels of free testosterone (P = 0.04), peak cardiac troponin (P = 0.03) were significantly higher and hs-CRP (P = 0.02) were lower in patients with complete ST-resolution compared to those with incomplete ST-resolution. In-hospital complications were observed in 31.2% of patients. The patients with a lower baseline TIMI flow (P = 0.03) and those who developed complications (P = 0.04) had lower levels of free testosterone. A significant positive correlation was observed between the left ventricular function and serum levels of free testosterone (P = 0.01 and r = +0.362).

Conclusion

This study suggests that in men with STEMI undergoing PPCI, higher serum levels of testosterone are associated with a better reperfusion response, fewer complications and a better left ventricular function.