Karsten Heyne

Prediction of Postoperative Outcome After Hepatectomy With a New Bedside Test for Maximal Liver Function Capacity

Objective:To validate the LiMAx test, a new bedside test for the determination of maximal liver function capacity based on 13C-methacetin kinetics. To investigate the diagnostic performance of different liver function tests and scores including the LiMAx test for the prediction of postoperative outcome after hepatectomy. Summary Background Data:Liver failure is a major cause of mortality after hepatectomy. Preoperative prediction of residual liver function has been limited so far. Methods:Sixty-four patients undergoing hepatectomy were analyzed in a prospective observational study. Volumetric analysis of the liver was carried out using preoperative computed tomography and intraoperative measurements. Perioperative factors associated with morbidity and mortality were analyzed. Cutoff values of the LiMAx test were evaluated by receiver operating characteristic. Results:Residual LiMAx demonstrated an excellent linear correlation with residual liver volume (r = 0.94, P < 0.001) after hepatectomy. The multivariate analysis revealed LiMAx on postoperative day 1 as the only predictor of liver failure (P = 0.003) and mortality (P = 0.004). AUROC for the prediction of liver failure and liver failure related death by the LiMAx test was both 0.99. Preoperative volume/function analysis combining CT volumetry and LiMAx allowed an accurate calculation of the remnant liver function capacity prior to surgery (r = 0.85, P < 0.001). Conclusions:Residual liver function is the major factor influencing the outcome of patients after hepatectomy and can be predicted preoperatively by a combination of LiMAx and CT volumetry.

Coherent low-frequency motions of hydrogen bonded acetic acid dimers in the liquid phase

Ultrafast vibrational dynamics of cyclic hydrogen bonded dimers and the underlying microscopic interactions are studied in temporally and spectrally resolved pump-probe experiments with 100 fs time resolution. Femtosecond excitation of the O-H and/or O-D stretching mode gives rise to pronounced changes of the O-H/O-D stretching absorption displaying both rate-like kinetic and oscillatory components. A lifetime of 200 fs is measured for the v=1 state of the O-H stretching oscillator. The strong oscillatory absorption changes are due to impulsively driven coherent wave packet motions along several low-frequency modes of the dimer between 50 and 170 cm(-1). Such wave packets generated via coherent excitation of the high-frequency O-H/O-D stretching oscillators represent a clear manifestation of the anharmonic coupling of low- and high-frequency modes. The underdamped low-frequency motions dephase on a time scale of 1-2 ps. Calculations of the vibrational potential energy surface based on density functional theory give the frequencies, anharmonic couplings, and microscopic elongations of the low-frequency modes, among them intermolecular hydrogen bond vibrations. Oscillations due to the excitonic coupling between the two O-H or O-D stretching oscillators are absent as is independently confirmed by experiments on mixed dimers with uncoupled O-H and O-D stretching oscillators.

Ultrafast dynamics of phytochrome from the cyanobacterium synechocystis, reconstituted with phycocyanobilin and phycoerythrobilin.

Femtosecond time-resolved transient absorption spectroscopy was employed to characterize for the first time the primary photoisomerization dynamics of a bacterial phytochrome system in the two thermally stable states of the photocycle. The 85-kDa phytochrome Cph1 from the cyanobacterium Synechocystis PCC 6803 expressed in Escherichia coli was reconstituted with phycocyanobilin (Cph1-PCB) and phycoerythrobilin (Cph1-PEB). The red-light-absorbing form Pr of Cph1-PCB shows an approximately 150 fs relaxation in the S(1) state after photoexcitation at 650 nm. The subsequent Z-E isomerization between rings C and D of the linear tetrapyrrole-chromophore is best described by a distribution of rate constants with the first moment at (16 ps)(-1). Excitation at 615 nm leads to a slightly broadened distribution. The reverse E-Z isomerization, starting from the far-red-absorbing form Pfr, is characterized by two shorter time constants of 0.54 and 3.2 ps. In the case of Cph1-PEB, double-bond isomerization does not take place, and the excited-state lifetime extends into the nanosecond regime. Besides a stimulated emission rise time between 40 and 150 fs, no fast relaxation processes are observed. This suggests that the chromophore-protein interaction along rings A, B, and C does not contribute much to the picosecond dynamics observed in Cph1-PCB but rather the region around ring D near the isomerizing C(15) [double bond] C(16) double bond. The primary reaction dynamics of Cph1-PCB at ambient temperature is found to exhibit very similar features as those described for plant type A phytochrome, i.e., a relatively slow Pr, and a fast Pfr, photoreaction. This suggests that the initial reactions were established already before evolution of plant phytochromes began.

Ultrafast coherent nuclear motions of hydrogen bonded carboxylic acid dimers

Abstract Real-time vibrational dynamics of the cyclic dimer of deuterated acetic acid in solution, a model system for hydrogen-bonded units of biomolecules, are elucidated by ultrafast infrared spectroscopy. Upon excitation of the O–D stretching mode, we demonstrate coherent nuclear motions along several intermolecular low-frequency modes of the dimer. The anharmonic coupling of the fast O–D stretching and slow low-frequency motions is isolated in the nonlinear vibrational response whereas other couplings are suppressed. The large-amplitude motions persist for several picoseconds, potentially allowing for optical control of (bio)chemical dynamics.

Real-Time Tracking of Phytochrome’s Orientational Changes During Pr Photoisomerization

Photoisomerization of a protein bound chromophore is the basis of the light sensing and signaling responses of many photoreceptors. Z-to-E photoisomerization of the Pr Cph1Δ2 phytochrome has been investigated by polarization resolved femtosecond visible pump-infrared probe spectroscopy, which yields structural information on the Pr excited (Pr*), Pr ground, and lumi-R product states. By exhaustive search analysis, two photoreaction time constants of (4.7 ± 1.4) and (30 ± 5) ps were found. Ring D orientational change in the electronic excited state to the transition state (90° twist) has been followed in real-time. Rotation of ring D takes place in the electronically excited state with a time constant of 30 ± 5 ps. The photoisomerization is best explained by a single rotation around C(15)═C(16) methine bridge in the Pr* state and a diffusive interaction with its protein surrounding.

Three-dimensional orientation of the Qy electronic transition dipole moment within the chlorophyll a molecule determined by femtosecond polarization resolved VIS pump-IR probe spectroscopy.

Chlorophyll a (Chl a) is the most abundant pigment on earth. In all plants, algae, and cyanobacteria, it plays a pivotal role as an antenna and reaction center pigment in the primary steps of photosynthesis. In the past, a true three-dimensional (3D) experimental determination of the Qy electronic transition dipole moment orientation could not be obtained. With combined femtosecond polarization resolved VIS pump-IR probe experiments and theoretical calculations of the infrared transition dipole moments (tdms) in the electronic ground state, we determined the 3D orientation of the Qy electronic tdm of Chl a within the molecular structure. Polarization resolved experiments provided angles of the Qy electronic tdm with three different infrared tdms, whose orientations within the molecular structure were taken from our theoretical calculations. The orientation of the Qy tdm results from the intersection of all three angles and was found to have an angle of (78 +/- 3)degrees with the x-axis, (12 3)degrees with the y-axis, and (86 +/- 2)degrees with the z-axis.

Photochemistry of Anthracene-9,10-endoperoxide

The wavelength dependence of the photochemistry of anthracene-9,10-endoperoxide (APO) in acetonitrile was quantitatively investigated at 5 degrees C, with excitation varied from 240 to 450 nm. Anthracene (AC) and a diepoxide (DE) were identified as the main primary photoproducts. After short exposure times DE was at all wavelengths the dominating photoproduct, while AC was only formed for lambda <or= 320 nm. The maximum AC quantum yield of 29% was reached at 270 nm. Anthraquinone (AQ) and a bicyclic acetal (BA) were identified as the main secondary products. Formation of AQ and BA occurred both from DE and from ground-state APO. Formation of BA from ground-state APO involved excited DE or BA itself, while formation of BA from DE required UV excitation of DE. Room-temperature thermolysis of APO only produced AQ. For lambda <or= 310 nm the total photochemistry quantum yield was, within error margins, constant and close to unity. Between 300 and 450 nm, the tail of the APO absorption spectrum, a more or less monotonic decrease of the total photochemistry quantum yield was observed.

Coherent vibrational dynamics of intermolecular hydrogen bonds in acetic acid dimers studied by ultrafast mid-infrared spectroscopy

Ultrafast vibrational motions and the underlying microscopic couplings in hydrogen-bonded cyclic dimers of acetic acid are studied by pump–probe and photon echo experiments in the mid-infrared. Upon femtosecond excitation of the O–H stretching mode, we demonstrate coherent nuclear motions along the in-plane dimer stretching mode which persist for picoseconds. The anharmonic coupling of the O–H stretching and the low-frequency mode is isolated in the nonlinear vibrational response, whereas other couplings are suppressed. Three-pulse photon echo experiments demonstrate a dephasing of O–H stretching excitations on a femtosecond timescale and quantum beats due to the anharmonically coupled dimer stretching mode.

Revealing Anharmonic Couplings and Energy Relaxation in DNA Oligomers by Ultrafast Infrared Spectroscopy

The identification and characterization of NH 2 hydrogen-bonded stretching vibrations [nu(NH 2)] in DNA oligomers is usually hampered by the all-dominating absorption of the water stretching band in the spectral range of 3050-3600 cm(-1). Here, we use the two-color IR pump-probe technique to overcome the limitations of linear absorption spectroscopy by exciting adenine-thymine (A-T) oligomer vibrations in the fingerprint region and analyzing induced transient spectral changes in the nu(NH2) spectral region. These transient changes are related to anharmonic couplings to the modes excited in the fingerprint region and to modes populated by intra- and intermolecular energy redistribution and relaxation. The combination of calculated anharmonic coupling parameters and experimental transient IR data allows the assignment of a transition at 3215 cm(-1) to the nu(NH2) vibration of adenine in dA(20)-dT(20) DNA oligomers.

Femtosecond polarization resolved spectroscopy: A tool for determination of the three-dimensional orientation of electronic transition dipole moments and identification of configurational isomers

A method is presented that combines femtosecond polarization resolved UV/visible pump-IR probe spectroscopy and density functional theory calculations in determining the three-dimensional orientation of an electronic transition dipole moment (tdm) within the molecular structure. The method is demonstrated on the approximately planar molecule coumarin 314 (C314) dissolved in acetonitrile, which can exist in two ground state configurations: the E- and the Z-isomer. Based on an exhaustive search analysis on polarization resolved measurement data for four different vibrational modes, it is concluded that C314 in acetonitrile is the E-isomer. The electronic tdm vector for the electronic S(0)-->S(1) transition is determined and the analysis shows that performing the procedure for four vibrational modes instead of the minimally required three reduces the 1sigma probability area from 2.34% to 2.24% of the solution space. Moreover, the fastest rotational correlation time tau(c) for the C314 E-isomer is determined to be 26+/-2 ps.