Michel Koch - Academia.edu (original) (raw)

Papers by Michel Koch

Zeitschrift für Naturforschung C, 1987

X-ray diffraction analysis of connective tissue samples, which contain type I and type III collag... more X-ray diffraction analysis of connective tissue samples, which contain type I and type III collagen shows that twisted collagen fibrils are a general principle of assembly. The occurrence of twisted fibrils in native wet Chordae tendineae, skin and Aorta is combined with a shorter axial periodicity of about 65 nm. This shorter D period is shown to be directly related to the tilt of the molecules, which have to be curved to build-up twisted fibrils.

Chemischer Informationsdienst, 1983

ChemInform Abstract 1H-NMR-und PE-spektroskopische Untersuchungen sowie EXAFS-Messungen an einem ... more ChemInform Abstract 1H-NMR-und PE-spektroskopische Untersuchungen sowie EXAFS-Messungen an einem Cu-Cystein-Schwefel-Protein, genannt Cu-Thionein, aus S. cerevisae zeigen, dass der einzelne Histidinrest nicht an der Koordination beteiligt ist und die Struktur am besten als cuban-ähnlich aus vier Cu(SR)2-Einheiten mit tetraedrischer Anordnung der Cystein-Schwefelatome am Cu bestehend,beschrieben werden kann.

Chemischer Informationsdienst. Organische Chemie, 1970

Physica B: Condensed Matter, 1997

The 70S ribosome from E.coli was analysed by neutron scattering focusing on the shape and the int... more The 70S ribosome from E.coli was analysed by neutron scattering focusing on the shape and the internal protein-RNA-distribution of the complex. Measurements on selectively deuterated 70S particles and free 30S and 50S subunits applying conventional contrast variation and proton-spin contrast-variation resulted in a total of 42 scattering curves. Processing the data on the basis of the spherical harmonic technique, a

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1992

Abstract The principle of a method for parallel readout of delay line detectors using a space-tim... more Abstract The principle of a method for parallel readout of delay line detectors using a space-time-space conversion is presented. It is shown that information processing in this system, which allows to process coincident events on pulsed sources like synchrotron radiation sources, is analogous to that in optical imaging systems. Preliminary results demonstrate the feasibility of the approach which also obviates the need for any external clock.

IEEE Transactions on Nuclear Science, 2000

This paper presents the software developments associated with the design and construction of a fa... more This paper presents the software developments associated with the design and construction of a fast wire per wire detector system that will be used for high-speed data collection of linear time-resolved X-ray diffraction spectra. As the overall hardware architecture of the system relies on the extensive use of a standard RISC based plug-in module, the code implementation of some critical

European Journal of Pharmaceutical Sciences, 1994

Angewandte Chemie International Edition in English, 1987

for the Mo, cluster and S=3/2 for the unique Mo atom. The Curie tail below 10 K is due to the pre... more for the Mo, cluster and S=3/2 for the unique Mo atom. The Curie tail below 10 K is due to the presence of a small amount (< 1%) of magnetic impurity. However, the exact nature of the broad maximum around 60 K in the plot of xm vs. T is still not clear to us. The assumption of a n unusual oxidation state (+ 3) for the unique Mo atom (Mo2) in 1 is supported by our recent discovery of CSMOP~O,,"'~ which is isostructural with KAIP20,Li21 and contains isolated Mo3+ ions in the oxygen lattice.

$Research paper thumbnail of Time-resolved X-ray diffraction study of structural changes associated with the photocycle of bacteriorhodopsin$

The EMBO Journal, 1991

The time course of structural changes accompanying the transition from the M412 intermediate to t... more The time course of structural changes accompanying the transition from the M412 intermediate to the BRCKQ ground state in the photocycle of bacteriorhodopsin (BR) from Halobacterium halobium was studied at room temperature with a time resolution of 15 ms using synchrotron radiation X-ray diffraction. The M412 decay rate was slowed down by employing mutated BR Asp96Asn in purple membranes at two different pHvalues. The observed light-induced intensity changes of in-plane X-ray reflections were fully reversible. For the mutated BR at neutral pH the kinetics of the structural alterations (r1i2 = 125 ms) were very similar to those of the optical changes characterizing the M412 decay, whereas at pH 9.6 the structural relaxation (T112 = 3 s) slightly lagged behind the absorbance changes at 410 nmn. The overall X-ray intensity change between the M412 intermediate and the ground state was about 9% for the different samples investigated and is associated with electron density changes close to helix G, B and E. Similar changes (r112 = 1.3-3.6 s), which also confirm earlier neutron scattering results on the BR_w and M412 intermediates trapped at-180°C, were observed with wild type BR retarded by 2 M guanidine hydrochloride (pH 9.4). The results unequivocally prove that the tertiary structure of BR changes during the photocycle.

Progress in Colloid & Polymer Science

Surfactant stabilized water/oil/water (w/o/w) double emulsions have received much attention in th... more Surfactant stabilized water/oil/water (w/o/w) double emulsions have received much attention in the last years motivated by their wide applications. Among double emulsions, those stabilized by phospholipids present special interest for their imitation of artificial cells, allowing the study of the effect of confining chemical reactions in biomimetic environments. Upon evaporation of the oil shell, phospholipid stabilized double emulsions can also serve as templates for giant vesicles. In this context, general assumptions have been made on the self-assembly and structural organization/arrangement of amphiphilic molecules, at the aqueous/oil liquid interface. However, to the best of our knowledge, no detailed evidence of the interfacial structuring have been reported. In this paper, w/o/w double emulsions formulated using the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and a mixture of chloroform and cyclohexane as the oil phase were produced using a microfluidic device. To obtain information on the phospholipid arrangement, the w/o/w interface was investigated by spatially resolved micro-focusing SAXS. We observed that (i) the basic units forming both the w/o and o/w interfaces were oil-swollen DMPC bilayers, arranged into a substantially disordered shell of $45 mm thickness surrounding the internal oil phase; (ii) the evaporation process was slow, i.e. in the order of one hour at 50 C and (iii) oil evaporation led to a shrinkage of the interfacial shell, but not to an increase of the ordering of the lipid bilayers. Interestingly, no stacked DMPC bilayers were observed during the evaporation process, as shown by the absence of Bragg's peaks in the SAXS intensity profiles.

Polymer, 2001

An alternating multiblock copolymer of poly(1-caprolactone) (PCL) and poly(hexamethylene terephth... more An alternating multiblock copolymer of poly(1-caprolactone) (PCL) and poly(hexamethylene terephthalate) (PHT) with a 48/52 PCL/PHT composition weight ratio has been synthesized. Its structural and morphological parameters were measured using 1 H NMR, density measurements, differential scanning calorimetry and its crystallization and melting were studied by real time simultaneous WAXS and SAXS using synchrotron radiation. These results are compared with those for the pure PCL and PHT used as building blocks. In the crystallization conditions used here, the copolymer crystallizes as alternate lamellae of PHT and PCL. The crystallinity of the PCL blocks is much lower than that of pure PCL because they crystallize under stress in the semi-crystalline PHT network.

Macromolecules, 1997

The annealing of poly(aryl ether ether ketone) (PEEK) from the glassy state was investigated by t... more The annealing of poly(aryl ether ether ketone) (PEEK) from the glassy state was investigated by time-resolved simultaneous small-angle (SAXS) and wide-angle (WAXS) X-ray scattering using synchrotron radiation and by differential scanning calorimetry (DSC). Each experiment consisted of a heating ramp from 100 °C to the annealing temperature (280, 300, 310, 315, 340, and 350 °C) at 10 °C/min, followed by a 30 min isotherm at this temperature and a cooling ramp down to 100 °C at −10 °C/min. The long spacing L and the invariant Q were estimated from the Lorentz-corrected SAXS intensity curves. The crystalline (Lc) and amorphous (La) thicknesses and the linear degree of crystallinity (vclin) within the stacks of lamellar crystals were obtained from the correlation function γ(r). The annealing temperature range can be divided into two regions based on the final morphology of the PEEK films. Samples annealed at temperatures up to 315 °C contain lamellar crystals that have crystallized during the isotherm. For an...

Macromolecules, 2006

... Raluca I. Gearba, § Denis V. Anokhin, § Alexander I. Bondar, Yuli K. Godovsky, Vladim... more ... Raluca I. Gearba, § Denis V. Anokhin, § Alexander I. Bondar, Yuli K. Godovsky, Vladimir S. Papkov, Natalia N. Makarova, Sergei N ... of Sciences, 28 Vavilov Str., 117813 Moscow, Russia, Veeco Metrology Group, 112 Robin Hill Road, Santa Barbara, California 93117 ...

Advanced Materials, 2005

Since their discovery, columnar mesophases have become increasingly important in fundamental rese... more Since their discovery, columnar mesophases have become increasingly important in fundamental research and in practi-cal applications[1,2] due to their peculiar supramolecular architectures that allow one-dimensional charge transport. Although the most studied columnar phases ...

Acta Crystallographica Section A Foundations of Crystallography, 2006

Biophysical Journal, 2002

Synthetic triacyl glucosamine monosaccharide lipid A part structures corresponding to the non-red... more Synthetic triacyl glucosamine monosaccharide lipid A part structures corresponding to the non-reducing moiety of enterobacterial lipid A with an acyloxyacyl chain linked to position 3 of the glucosamine and an unbranched chain linked to position 2 (group 1) and vice versa (group 2) were analyzed biophysically: Fourier-transform infrared spectroscopy was performed to characterize the gel-to-liquid crystalline phase transition, the phosphate band contour, and the orientation of the glucosamine with respect to the membrane surface. Small-angle x-ray diffraction was applied for the elucidation of the supramolecular aggregate structure and, with that, of the molecular shape. With fluorescence resonance energy transfer the lipopolysaccharide-binding protein (LBP)-mediated intercalation of the lipid A partial structures into phospholipid liposomes was monitored. The physical data clearly exhibit a classification of the synthetic compounds into two groups: group 1 compounds have sharp phase transitions, indicating dense acyl chain packing and an inclination of the glucosamine backbone with respect to the membrane surface of 30°with the phosphate buried in the membrane. Group 2 compounds have a very broad phase transition, indicating poorly packed acyl chains, and an inclination of Ϫ30°with the phosphate group sticking outward. For the first group unilamellar phases are observed superimposed by a non-lamellar structure, and for the second one only multilamellar aggregate structures. The cytokine-inducing capacity in human mononuclear cells is relatively high for the first group and low or absent for the second group. Based on these data a model of the intra and intermolecular conformations is proposed which also extends the concept of "endotoxic conformation."

Chemistry of Materials, 2004

Solvents and reagents were purchased from Aldrich and used as received. Column chromatographies w... more Solvents and reagents were purchased from Aldrich and used as received. Column chromatographies were performed on silica gel (Merck silica gel 60, mesh size 0.2-0.5 mm). NMR spectra were recorded in CDCl 3 on a Bruker Avance 300 with solvent signal as internal standard. Mass spectra were recorded on a Finnigan MAT 95 instrument (FD-MS) and a Bruker Reflex (MALDI-TOF). Elemental Analysis were done in the Microlab of the University of Mainz. 4'-(3,4,5-Tridodecyloxybenzoyloxy)benzoic acid 4a, 4'-[4''-(3,4,5-Tridodecyloxybenzoyloxy)benzoyloxy]benzoic acid 4b were synthesized by modifying the procedure of reference [1], using N,Ndimethyl-4-aminopyridinium 4-toluenesulfonate (DPTS) instead of N,N-dimethyl-4-aminopyridin (DMAP). The thermal behaviour of all the materials synthesized was investigated by POM (Olympus Provis microscope equipped with a Mettler FP 82 heating stage and a Jena microscope equipped with a Mettler FP52 hot stage) and DSC (Mettler Toledo DSC 821) with heating and cooling scans performed at 10 °C/min. X-ray diffraction experiments were performed on the X33 camera of the European Molecular Biology Laboratory at the storage ring DORIS III of the Deutsches Elektronen Synchrotron (DESY), Hamburg. Diffraction patterns were collected in transmission in series of frames of 6s each with two position sensitive delay line readout detectors connected in series. 2 The sample temperature