Proteolytic Fragments of Chromogranins A and B Represent Major Soluble Components of Chromaffin Granules, Illustrated by Two-Dimensional Proteomics with NH2-Terminal Edman Peptide Sequencing and MALDI-TOF MS
BIOCHEMISTRY
Authors: Lee, Jean C.; Hook, Vivian
Abstract
Neuroendocrine chromaffin granules of adrenal medulla represent regulated secretory vesicles that secrete neuropeptides and catecholamines which mediate cell-cell communication for physiological functions. This study addressed the identification of the major proteins in these secretory vesicles that provide dynamic storage and secretion of bioactive molecules. Proteins of the soluble compartment of the vesicles were separated by two-dimensional gels and subjected to NH2-terminal Edman sequencing for identification and determination of NH2-termini. Results showed that proteolytic fragments of chromogranin A (CgA) and chromogranin B (CgB) represent the major proteins of these secretory vesicles. These fragments resulted from cleavage of their respective precursor proteins at dibasic and monobasic sites, which is consistent with the known cleavage specificities of prohormone processing enzymes. MALDI-TOF MS analyses of protein spots similar in molecular weight that possessed a range of pI values were represented by molecular forms of CgA and CgB proteins. These findings indicate the high prevalence of endogenous CgA and CgB proteolytic fragments that function in chromaffin secretory vesicles for release of bioactive molecules for cell-cell communication.
Er, Yb:Ca3RE2(BO3)(4) (RE=Y, Gd) - Novel 1.5 mu m Laser Crystals
DEVICES AND METHODS OF MEASUREMENTS
Authors: Gorbachenya, K. N.; Deineka, R., V; Kisel, V. E.; Yasukevich, A. S.; Shekhovtsov, A. N.; Kosmyna, M. B.; Kuleshov, N., V
Abstract
The search for new crystalline host materials for the usage in lasers emitting in the eye-safe spectral range of 1.5-1.6 mu m is an important task. The aim of this work was to study the growth technique, spectroscopic properties and laser characteristics of new active media - crystals Er3+,Yb3+: Ca3RE2(BO3)(4) (RE=Y, Gd). Calcium-yttrium Er3+, Yb3+: Ca3Y2(BO3)(4) (CYB) and calcium-gadolinium Er3+, Yb3+: Ca3Gd2(BO3)(4) (CGB) oxoborate crystals co-doped with erbium and ytterbium ions were investigated. Polarized absorption and emission cross-section spectra were determined. The lifetimes of I-4(11/2) and I-4(13/2) energy levels of Er3+ ions were measured and ytterbium-erbium energy transfer efficiencies were estimated. The calculation of the gain cross-section spectra was performed. By using of Er3+, Yb3+: Ca3RE2(BO3)(4) (RE=Y, Gd) crystals the laser performance was realized, for the first time to the best of our knowledge. The laser characteristics were studied in a quasi-CW (QCW) laser operation. The wide band with a peak at the wavelength of 976 nm is observed in the absorption spectra of both crystals. This peak coincides with the emission wavelength of the pump laser diodes for Yb-doped active media. The maximum value of absorption cross-section was 1.7 x 10(-20) cm(2) for polarization E // b for both crystals. The lifetimes of the upper laser level I-4(13/2) of Er3+ ions were 580 +/- 30 mu s and 550 +/- 30 mu s for Er, Yb: CYB and Er, Yb: CGB crystals, respectively. The energy transfer efficiencies from ytterbium to erbium ions for an Er, Yb: CYB and Er, Yb: CGB crystals were 94 % and 96 %, respectively. According to gain spectrum of the Er, Yb: CYB crystal the gain band peak is centered at the wavelength of 1530 nm. The maximum QCW output power was 0.5 W with slope efficiency of 13 % regarding to absorbed pump power for an Er, Yb: CYB crystal. The laser beam parameter M-2 did not exceed < 1.5. Based on the obtained results, it can be concluded that these crystals are promising active media for lasers emitting in the spectral range of 1.5-1.6 mu m for the usage in laser rangefinder and laser-induced breakdown spectroscopy systems, and LIDARs.