228 research outputs found
High-spin low-spin transition
Temperature dependent nuclear inelastic-scattering (NIS) of synchrotron
radiation was applied to investigate both spin states of the spin-crossover
complex [Fe(tpa)(NCS)(2)] (tpa = tris(2-pyridylmethyl)amine). A remarkable
increase of the iron-ligand bond stretching upon spin crossover has
unambiguously been identified by comparing the measured NIS spectra with
theoretical simulations based on density-functional calculations
Density functional theory calculations and vibrational spectroscopy on iron spin-crossover compounds
Iron complexes with a suitable ligand field undergo spin-crossover (SCO),
which can be induced reversibly by temperature, pressure or even light.
Therefore, these compounds are highly interesting candidates for optical
information storage, for display devices and pressure sensors. The SCO
phenomenon can be conveniently studied by spectroscopic techniques like Raman
and infrared spectroscopy as well as nuclear inelastic scattering, a technique
which makes use of the M\"ossbauer effect. This review covers new developments
which have evolved during the last years like, e.g. picosecond infrared
spectroscopy and thin film studies but also gives an overviewon newtechniques
for the theoretical calculation of spin transition phenomena and vibrational
spectroscopic data of SCO complexes
Pressure-induced changes of the vibrational modes of spin-crossover complexes studied by nuclear resonance scattering of synchrotron radiation
Nuclear inelastic scattering (NIS) spectra were recorded for the
spin-crossover complexes STP and ETP (STP =
[Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg- ethane)](ClO4)2 and
ETP =
[Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg-butane)](ClO4)2) at
30 K and at room temperature and also at ambient pressure and applied pressure
(up to 2.6 GPa). Spin transition from the high-spin (HS) to the low-spin (LS)
state was observed by lowering temperature and also by applying pressure at
room temperature and has been assigned to the hardening of iron-bond stretching
modes due to the smaller volume in the LS isomer
Nuclear Resonance Vibrational Spectroscopy of Iron Sulfur Proteins
Nuclear inelastic scattering in conjunction with density functional theory
(DFT) calculations has been applied for the identification of vibrational modes
of the high-spin ferric and the high-spin ferrous iron-sulfur center of a
rubredoxin-type protein from the thermophylic bacterium Pyrococcus abysii
DFT Calculations as a Tool to Analyse Quadrupole Splittings of Spin Crossover Fe(II) complexes
Density functional methods have been applied to calculate the quadrupole
splitting of a series of iron(II) spin crossover complexes. Experimental and
calculated values are in reasonable agreement. In one case spin-orbit coupling
is necessary to explain the very small quadrupole splitting value of 0.77 mm/s
at 293 K for a high-spin isomer
Dynamics of Metal Centers Monitored by Nuclear Inelastic Scattering
Nuclear inelastic scattering of synchrotron radiation has been used now since
10 years as a tool for vibrational spectroscopy. This method has turned out
especially useful in case of large molecules that contain a M\"ossbauer active
metal center. Recent applications to iron-sulfur proteins, to iron(II) spin
crossover complexes and to tin-DNA complexes are discussed. Special emphasis is
given to the combination of nuclear inelastic scattering and density functional
calculations
M\"ossbauer, nuclear inelastic scattering and density functional studies on the second metastable state of Na2[Fe(CN)5NO]2H2O
The structure of the light-induced metastable state SII of
Na2[Fe(CN)5NO]2H2O 14 was investigated by transmission M\"ossbauer
spectroscopy (TMS) in the temperature range 15 between 85 and 135 K, nuclear
inelastic scattering (NIS) at 98 K using synchrotron 16 radiation and density
functional theory (DFT) calculations. The DFT and TMS results 17 strongly
support the view that the NO group in SII takes a side-on molecular orientation
18 and, further, is dynamically displaced from one eclipsed, via a staggered,
to a second 19 eclipsed orientation. The population conditions for generating
SII are optimal for 20 measurements by TMS, yet they are modest for
accumulating NIS spectra. Optimization 21 of population conditions for NIS
measurements is discussed and new NIS experiments on 22 SII are proposed
Y-box protein-1/p18 fragment identifies malignancies in patients with chronic liver disease
<p>Abstract</p> <p>Background</p> <p>Immunohistochemical detection of cold shock proteins is predictive for deleterious outcome in various malignant diseases. We recently described active secretion of a family member, denoted Y-box (YB) protein-1. We tested the clinical and diagnostic value of YB-1 protein fragment p18 (YB-1/p18) detection in blood for malignant diseases.</p> <p>Methods</p> <p>We used a novel monoclonal anti-YB-1 antibody to detect YB-1/p18 by immunoblotting in plasma samples of healthy volunteers (n = 33), patients with non-cancerous, mostly inflammatory diseases (n = 60), hepatocellular carcinoma (HCC; n = 25) and advanced solid tumors (n = 20). YB-1/p18 was then tested in 111 patients with chronic liver diseases, alongside established tumor markers and various diagnostic measures, during evaluation for potential liver transplantation.</p> <p>Results</p> <p>We developed a novel immunoblot to detect the 18 kD fragment of secreted YB-1 in human plasma (YB-1/p18) that contains the cold-shock domains (CSD) 1-3 of the full-length protein. YB-1/p18 was detected in 11/25 HCC and 16/20 advanced carcinomas compared to 0/33 healthy volunteers and 10/60 patients with non-cancerous diseases. In 111 patients with chronic liver disease, YB-1/p18 was detected in 20 samples. Its occurrence was not associated with advanced Child stages of liver cirrhosis or liver function. In this cohort, YB-1/p18 was not a good marker for HCC, but proved most powerful in detecting malignancies other than HCC (60% positive) with a lower rate of false-positive results compared to established tumor markers. Alpha-fetoprotein (AFP) was most sensitive in detecting HCC, but simultaneous assessment of AFP, CA19-9 and YB-1/p18 improved overall identification of HCC patients.</p> <p>Conclusions</p> <p>Plasma YB-1/p18 can identify patients with malignancies, independent of acute inflammation, renal impairment or liver dysfunction. The detection of YB-1/p18 in human plasma may have potential as a tumor marker for screening of high-risk populations, e.g. before organ transplantation, and should therefore be evaluated in larger prospective studies.</p
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