[Hereditary skeletal dysplasias and FGFR3 and PTHR1 signaling pathways].

Skeletal development is a highly sophisticated process involving, as a first step, migration and condensation of mesenchymal cells into osteoprogenitor cells. These cells further differentiate into chondrocytes and osteoblasts through multiple differentiation stages requiring a set of specific transcriptional factors. Defective endochondral ossification in human is associated with a large number of inherited skeletal dysplasias caused by mutations in genes encoding extracellular matrix components, growth factors and their receptors, signaling molecules and transcription factors.

Adaptation of a PAM-fluorometer for remote sensing of chlorophyll fluorescence.

The Laser-PAM described in this paper is an adaptation of the PAM 101 fluorometer (Heinz Walz, Effeltrich, Germany) designed for remote sensing and non-invasive laboratory measurements of chlorophyll fluorescence. It is based on a 5 mW laser diode, emitting at 638 nm, and a Fresnel lens coupled to the ED-101 detection unit. Due to these modifications, measurements can be performed at a distance ranging from 0.

Photoinactivation of the photosynthetic electron transport chain by accumulation of over-saturating light pulses given to dark adapted pea leaves.

The effect of cumulative over-saturating pulses (OSP) of white light (1 s, >10 000 mumol photons m(-2) s(-1)), applied every 20 min on pea leaves, was investigated during a complete diurnal cycle of 24 h. In dark-adapted leaves, this treatment leads to a progressive decline of the optimum Photosystem II (PS II) quantum yield. Continuous low background light (except far-red light) had a protective effect against this OSP-induced photoinactivation.

Photoionization of synchrotron-radiation-excited atoms: separating partial cross sections by full polarization control.

Resonant atomic excitation by synchrotron radiation and subsequent ionization by a tunable dye laser is used to study the photoionization of short-lived Rydberg states in Xe. By combining circular and linear polarization of the synchrotron as well as of the laser photons the partial photoionization cross sections were separated in the region of overlapping autoionizing resonances of different symmetry and the parameters of the resonances were extracted.

Urate oxidase from Aspergillus flavus: new crystal-packing contacts in relation to the content of the active site.

Urate oxidase from Aspergillus flavus (uricase or Uox; EC 1.7.3.

The crystal structure of annexin A8 is similar to that of annexin A3.

Annexin A8 is a relatively infrequent and poorly studied member of this large family of calcium-binding and membrane-binding proteins. It is, however, associated with a specific disease, acute promyelocytic leukemia. We have solved its three-dimensional structure, which includes a moderately long and intact N terminus.

Dualex: a new instrument for field measurements of epidermal ultraviolet absorbance by chlorophyll fluorescence.

Dualex (dual excitation) is a field-portable instrument, hereby described, for the assessment of polyphenolic compounds in leaves from the measurement of UV absorbance of the leaf epidermis by double excitation of chlorophyll fluorescence. The instrument takes advantage of a feedback loop that equalizes the fluorescence level induced by a reference red light to the UV-light-induced fluorescence level. This allows quick measurement from attached leaves even under field conditions.

Calcium-dependent self-assembly of human centrin 2.

Human centrin 2 (HsCen2) is a member of the EF-hand superfamily of calcium-binding proteins, often associated with the centrosomes and basal bodies. These organelles exhibit different morphological aspects, including a variety of centrin-containing fibers that connect the two centrioles or other structural elements of the pericentriolar space. The molecular basis of the Ca(2+)-sensitive fibers and their precise role in centrosome duplication are not known.

New aspects of the alpha-helix to beta-sheet transition in stretched hard alpha-keratin fibers.

The putative transformation of alpha-helices into beta-sheets has been studied for more than 50 years in the case of hard alpha-keratin. In a previous study of stretched keratin fibers, we specified the conditions for beta-sheet appearance within horsehair: the formation of beta-sheets requires at least 30% relative humidity. However, this phenomenon was observed in the whole tissue.

Correlation between lifetime heterogeneity and kinetics heterogeneity during chlorophyll fluorescence induction in leaves: 2. Multi-frequency phase and modulation analysis evidences a loosely connected PSII pigment-protein complex.

We report the first direct decomposition of the fluorescence lifetime heterogeneity during multiphasic fluorescence induction in dark-adapted leaves by multi-frequency phase and modulation fluorometry (PMF). A very fast component, assigned to photosystem I (PSI), was found to be constant in lifetime and yield, whereas the two slow components, which are strongly affected by the closure of the reaction centers by light, were assigned to PSII. Based on a modified "reversible radical pair" kinetic model with three compartments, we showed that a loosely connected pigment complex, which is assumed to be the CP47 complex, plays a specific role with respect to the structure and function of the PSII: (i) it explains the heterogeneity of PSII fluorescence lifetime as a compartmentation of excitation energy in the antenna, (ii) it is the site of a conformational change in the first second of illumination, and (iii) it is involved in the mechanisms of nonphotochemical quenching (NPQ).

Correlation between lifetime heterogeneity and kinetics heterogeneity during chlorophyll fluorescence induction in leaves: 1. Mono-frequency phase and modulation analysis reveals a conformational change of a PSII pigment complex during the IP thermal phase.

The relationship between the fluorescence lifetime (tau) and yield (Phi) obtained in phase and modulation fluorometry at 54 MHz during the chlorophyll fluorescence induction in dark-adapted leaves under low actinic light has been investigated. Three typical phases have been identified: (i) linear during the OI photochemical rise, (ii) convex curvature during the subsequent IP thermal rise, and (iii) linear during the PS slow decay. A similar relationship has been obtained in the fluorescence induction for the fluorescence yield measured at 685 nm plotted versus the fluorescence yield measured at 735 nm.

The intermediate filament architecture as determined by X-ray diffraction modeling of hard alpha-keratin.

Despite investigation since the 1950s, the molecular architecture of intermediate filaments has not yet been fully elucidated. Reliable information about the longitudinal organization of the molecules within the filaments and about the lateral interfilament packing is now available, which is not the case for the transverse architecture. Interesting results were recently obtained from in vitro microscopy observations and cross-linking of keratin, desmin, and vimentin analyses.

Complexed and ligand-free high-resolution structures of urate oxidase (Uox) from Aspergillus flavus: a reassignment of the active-site binding mode.

High-resolution X-ray structures of the complexes of Aspergillus flavus urate oxidase (Uox) with three inhibitors, 8-azaxanthin (AZA), 9-methyl uric acid (MUA) and oxonic acid (OXC), were determined in an orthorhombic space group (I222). In addition, the ligand-free enzyme was also crystallized in a monoclinic form (P2(1)) and its structure determined. Higher accuracy in the three new enzyme-inhibitor complex structures (Uox-AZA, Uox-MUA and Uox-OXC) with respect to the previously determined structure of Uox-AZA (PDB code 1uox) leads to a reversed position of the inhibitor in the active site of the enzyme.

Imaging capabilities of synchrotron infrared microspectroscopy.

It has become increasingly clear that synchrotron infrared micro-spectroscopy is an extremely valuable analysis tool when determining the chemical composition of biological and biomedical samples, at the diffraction-limited spatial resolution. Highly resolved infrared micro-spectroscopy, together with the high signal-to-noise level of the recorded spectra, is essential in generating chemical and statistical (multivariate) images. This is illustrated in the case of individual cell and hair section studies.

X-ray synchrotron study of liquid-vapor interfaces at short length scales: effect of long-range forces and bending energies.

We have investigated the small-scale structure of the liquid-vapor interface using synchrotron x-ray scattering for liquids with different molecular structures and interactions. The effective momentum-dependent surface energy first decreases from its macroscopic value due to the effect of long-range forces, and then increases with increasing wave vector. The results are analyzed using a recent density functional theory.

Phasing power at the K absorption edge of organic arsenic.

Single/multiple-wavelength anomalous dispersion (SAD/MAD) experiments were performed on a crystal of an organic arsenic derivative of hen egg-white lysozyme. A para-arsanilate compound used as a crystallizing reagent was incorporated into the ordered solvent region of the lysozyme molecule. Diffraction data were collected to high resolution ( View Article and Find Full Text PDF

Biological and biomedical applications of synchrotron infrared microspectroscopy.

The high brightness of synchrotron light,which is about three orders of magnitudegreater than a thermal source, has beenexploited in biological and biomedicalapplications of infrared microspectroscopy. The potential of this analytical tool isdocumented in this article in the study ofhuman tissue (hair and skin) and individualcells: biochemical and bio-structuralchanges based on corresponding functionalgroups have been identified and imaged withunprecedented spatial resolution. Thistechnique also provides a new tool foranalysis of biochemical kinetics of samplesduring disease and treatment.

Circular polarization of ion fluorescence completing the analysis of resonant Xe* 4d(-1)(5/2)6p Auger decay.

The relative contributions of the partial electron waves emitted in the Auger decay of the Xe* 4d(-1)(5/2)6p(J(*)=1) resonance have been determined by fluorescence polarimetry after excitation with circularly polarized synchrotron radiation. The analysis of circularly polarized fluorescence of the photoion leads to an independent determination of the orientation parameters for all states of the Xe II 5p(4)6p multiplet. The present study provides, in combination with data on the angular distribution and spin polarization of the Auger electrons, complete quantum mechanical information on the resonant Auger decay, i.

UV-induced blue-green and far-red fluorescence along wheat leaves: a potential signature of leaf ageing.

Under UV-excitation, leaves emit red (RF) and far-red (FRF) fluorescence from chlorophyll and blue-green fluorescence (BGF) from hydroxycinnamic acids. In this study, the aim was to develop a fluorescence signature of wheat leaf ageing after the emergence of the lamina. FRF and BGF were examined in the first three leaves of 2-week-old wheat plants.

The structural basis for catalysis and specificity of the X-prolyl dipeptidyl aminopeptidase from Lactococcus lactis.

The X-prolyl dipeptidyl aminopeptidase (X-PDAP) from Lactococcus lactis is a dimeric enzyme catalyzing the removal of Xaa-Pro dipeptides from the N terminus of peptides. The structure of the enzyme was solved at 2.2 A resolution and provides a model for the peptidase family S15.

Importance of the nature of anions in lysozyme crystallisation correlated with protein net charge variation.

Hofmeister anion series are studied to examine the coupled influence of pH and ionic strength on the solubility of previously desalted lysozyme. Solubility curves are measured at pH 4.3 and 8.

A procedure for refining a coiled coil protein structure using x-ray fiber diffraction and modeling.

We describe a combined use of experimental and simulation techniques to configure side chains in a coiled coil structure. As already demonstrated in a previous work, x-ray diffraction patterns from hard alpha-keratin fibers in the 5.15 A meridian zone reflect the global configuration of the chi(1) dihedral angle of the coiled coil side chains.

Ca(2+) and membrane binding to annexin 3 modulate the structure and dynamics of its N terminus and domain III.

Annexin 3 (ANX A3) represents approximately 1% of the total protein of human neutrophils and promotes tight contact between membranes of isolated specific granules in vitro leading to their aggregation. Like for other annexins, the primary molecular events of the action of this protein is likely its binding to negatively charged phospholipid membranes in a Ca(2+)-dependent manner, via Ca(2+)-binding sites located on the convex side of the highly conserved core of the molecule. The conformation and dynamics of domain III can be affected by this process, as it was shown for other members of the family.

Strong, polarized Balmer-alpha fluorescence after resonant core excitation of HCl.

Visible-UV fluorescence has been analyzed after resonant Cl 2p core excitation of HCl molecules. The dispersed fluorescence spectra are dominated by emissions from atomic fragments. In particular, an intense and polarized Balmer H(alpha) line is observed after photoexcitation of the 2p(-1)nl Rydberg states.