110 research outputs found
The Synthesis of B-Hydroxytryptamines
It might be expected that B-hydroxylation of the side chain of tryptamine,
5-hydroxytryptamine (serotonin) and 5-methoxytryptamine would be of biological importance as it is the case with phenylethylamine group of biogenic amines (cf. tyramine-octopamine, dopamine-noradrenaline)
Chromatography of Indole Derivatives on Sephadex G-15
The chromatographic · properties of indole derivatives, mainly
biogenetically related to the plant growth hormone, indole-3-acetic
acid, were studied on Sephadex G-15. The eluents used were 70°/o
and 30°/o aqueous methanol, volatile ethylenediamine-acetate buffers
of pH 4.2 and 7.4, and distilleo water adjusted to pH 7.4. The
adsorption of indole derivatives to Sephadex could be preferentially
ascribed to the heterocyclic nucleus which is bound by rt complex
formation, as well as by hydrogen and hydrophobic bonding. The
presence of a side chain, if subject to the same type of binding
forces, results not only in stronger sorption but also in some exclusion
in accordance with molecular weight. Furthermore, because
of the carboxyl groups contained in Sephadex gels, positively charged
compounds are bound by ion exchange, whereas negatively
charged ones are acted upon by Donnan ion exclusion forces
Beta-hydroxytryptamines. I. Chemical Synthesis of 3-(2-Amino- 1-hydroxyethyl)indole and 5-Hydroxy-3-(2-amino-l-Hydroxy-ethyl)indole
From indole and 5-benzyloxyindole, respectively, the corresponding
chloromethyl 3-indolyl ketones were prepared applying
Guignard reaction with chloroacetyl chloride or Vilsmeier reaction
with N,N-diethylchloroacetamide. By i. r. and n. m. r. spectroscopy
it was proved that identical compounds were obtained in both
reactions.
After the substitution of the halide with dibenzylamino group
and the reduction of the carbonyl group to hydroxyl with lithium
alumi.num hydride, benzyl groups were removed by catalytic
hydrogenation.
3-(2-Amino-1-hydroxyethy l)indole (beta-hydroxytryptamine)
and 5-hydroxy-3-(2-amino-1-hydroxyethyl)indole (beta-hydroxyserotonin)
were isolated in the form of crystalline creatinine
sulphates. Solubility and satisfying stability in aqueous solutions
make these salts suitable for biochemical and pharmaco\u27logical
investigations
Zinc Sulfide Tubes Reinforced with Carbon Nanofibers
Zinc sulfide submicron and nanotubes with outer diameters in the range from 100 to 1000 nm were produced through chemical deposition from vapor under argon pressure. The novel process provides formation of ZnS tubes reinforced with carbon nanofibers. This is the first time that the ZnS tubes are grown with fibers during deposition
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RECRYSTALLIZATION OF CERAMIC MATERIAL FABRICATED FROM Cd1-xZnxTe.
Binary and ternary A(illegible)B(illegible) compounds are conventionally grown from melt. This technique is very complicated and requires complex equipment to provide high pressures and high temperatures to grow stoichiometric compositions. New opportunities for designing materials used in the infrared technique and ionizing radiation detectors are opened by advantages in nanotechnology. In particular difficulties in Cd{sub 1-x}Zn{sub x}Te with various Zn content are traditionally used in infrared optics and as a material for ionizing radiation detectors. Zn concentration in the nanopowders produced by the new vapor deposition technique varies from x=0.02 to x=0.1, including the composition Cd{sub illegible}Zn{sub illegible}Te, which is the most promising as a material for ionizing radiation detectors working at room temperature without cooling
Magnetic Resonance of the Intrinsic Defects of the Spin-Peierls Magnet CuGeO3
ESR of the pure monocrystals of CuGeO3 is studied in the frequency range 9-75
GHz and in the temperature interval 1.2-25 K. The splitting of the ESR line
into several spectral components is observed below 5 K, in the temperature
range where the magnetic susceptibility is suppressed by the spin-Peierls
dimerization. The analysis of the magnetic resonance signals allows one to
separate the signals of the S=1/2- and S=1 defects of the spin-Peierls phase.
The value of g-factor of these signals is close to that of the Cu-ion. The
additional line of the magnetic resonance is characterized by an anomalous
value of the g-factor and by the threshold-like increase of the microwave
susceptibility when the microwave power is increasing. The ESR signals are
supposingly attributed to two types of the planar magnetic defects, arising at
the boundaries of the domains of the spin-Peierls state with the different
values of the phase of the dimerization.Comment: LATEX-text, 12 PS-figures, typos corrected, LATEX-style change
Effect of the spin-orbit interaction on the band structure and conductance of quasi-one-dimensional systems
We discuss the effect of the spin-orbit interaction on the band structure,
wave functions and low temperature conductance of long quasi-one-dimensional
electron systems patterned in two-dimensional electron gases (2DEG). Our model
for these systems consists of a linear (Rashba) potential confinement in the
direction perpendicular to the 2DEG and a parabolic confinement transverse to
the 2DEG. We find that these two terms can significantly affect the band
structure introducing a wave vector dependence to subband energies, producing
additional subband minima and inducing anticrossings between subbands. We
discuss the origin of these effects in the symmetries of the subband wave
functions.Comment: 15 pages including 14 figures; RevTeX; to appear in Phys.Rev.B (15
Nov 1999
Dynamical spin-electric coupling in a quantum dot
Due to the spin-orbital coupling in a semiconductor quantum dot, a freely
precessing electron spin produces a time-dependent charge density. This creates
a sizeable electric field outside the dot, leading to promising applications in
spintronics. The spin-electric coupling can be employed for non-invasive single
spin detection by electrical methods. We also consider a spin relaxation
mechanism due to long-range coupling to electrons in gates and elsewhere in the
system, and find a contribution comparable to, and in some cases dominant over
previously discussed mechanisms.Comment: 4 pages, 2 figure
Circularly polarized electroluminescence from silicon nanostructures heavily doped with boron
The circularly polarized electroluminescence (CPEL) from silicon
nanostructures which are the p-type ultra-narrow silicon quantum well (Si-QW)
confined by {\delta}-barriers heavily doped with boron, 5 10^21 cm^-3, is under
study as a function of temperature and excitation levels. The CPEL dependences
on the forward current and temperature show the circularly polarized light
emission which appears to be caused by the exciton recombination through the
negative-U dipole boron centers at the Si-QW {\delta}-barriers interface
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