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Osteocalcin is the most abundant noncollagenous protein in bone 1 , and its concentration in serum is closely linked to bone metabolism and serves as a biological marker for the clinical assessment of bone disease 2 . Although its precise mechanism of action is unclear, osteocalcin influences bone mineralization 3 , 4 , in part through its ability to bind with high affinity to the mineral component of bone, hydroxyapatite 5 . In addition to binding to hydroxyapatite, osteocalcin functions in cell signalling and the recruitment of osteoclasts 6 and osteoblasts 7 , which have active roles in bone resorption and deposition, respectively. Here we present the X-ray crystal structure of porcine osteocalcin at 2.0 Å resolution, which reveals a negatively charged protein surface that coordinates five calcium ions in a spatial orientation that is complementary to calcium ions in a hydroxyapatite crystal lattice. On the basis of our findings, we propose a model of osteocalcin binding to hydroxyapatite and draw parallels with other proteins that engage crystal lattices.

Filming atomic motion within molecules is an active pursuit of molecular physics and quantum chemistry. A promising method is laser-induced Coulomb Explosion Imaging (CEI) where a laser pulse rapidly ionizes many electrons from a molecule, causing the remaining ions to undergo Coulomb repulsion. The ion momenta are used to reconstruct the molecular geometry which is tracked over time (i.e., filmed) by ionizing at an adjustable delay with respect to the start of interatomic motion. Results are distorted, however, by ultrafast motion during the ionizing pulse. We studied this effect in water and filmed the rapid “slingshot” motion that enhances ionization and distorts CEI results. Our investigation uncovered both the geometry and mechanism of the enhancement which may inform CEI experiments in many other polyatomic molecules. Laser-induced Coulomb explosion imaging allows the study of molecular geometries over time, but the results are often distorted by ultrafast motion during the ionizing laser pulse. Here, the authors film the rapid slingshot motion in D 2 O that induces this distortion and elucidate the underlying mechanism of enhanced ionization.

It is a truism that physical disabilities should not be barriers to success in scientific endeavors, but the reality is that disabilities can be hindrances to success in research. In the ACA we focus on structural science, so I want to draw attention to specific ways that physical disabilities hinder progress in structural science. Blindness, deafness, and limitations in mobility can interfere with effectiveness at the lab bench and even in the computer lab. Less all-encompassing disabilities, such as color-blindness and tremors, can become hindrances—sometimes because of the nature of the tasks, and sometimes because of the conventions by which scientists communicate with one another. I will explore the hindrances, large and small, and the ways that structural scientists can help one another overcome them.

The proportion of patients who had preoperative heart rate and blood pressure measurements was 78%. Verification studies are required.Disclosures None.Acknowledgements We would like to thank the staff at the St George Medical Records Department for their invaluable help with this study.Conflicts of interest None.Funding None.Prior presentation None. Frequency Nil by mouth No reason given Not charted Preparation for TOE-cardioversion SBP 101 mm Hg and HR 51bpma Not available Total 5 (33%) 5 (33%) 2 (13%) 1 (7%) 1 (7%) 1 (7%) 15 (100%) Table 1 Reasons for inappropriately withholding beta-blockers.

Structural imaging of transient excited-state species is a key goal of molecular physics, promising to unveil rich information about the dynamics underpinning photochemical transformations. However, separating the electronic and nuclear contributions to the spectroscopic observables is challenging, and typically requires the application of high-level theory. Here, we employ site-selective ionisation via ultrashort soft X-ray pulses and time-resolved Coulomb explosion imaging to interrogate structural dynamics of the ultraviolet photochemistry of carbon disulfide. This prototypical system exhibits the complex motifs of polyatomic photochemistry, including strong non-adiabatic couplings, vibrational mode couplings, and intersystem crossing. Immediately following photoexcitation, we observe Coulomb explosion signatures of highly bent and stretched excited-state geometries involved in the photodissociation. Aided by a model to interpret such changes, we build a comprehensive picture of the photoinduced nuclear dynamics that follows initial bending and stretching motions, as the reaction proceeds towards photodissociation. Coulomb Explosion imaging is a promising technique to study the ultrafast nuclear dynamics which underpin molecular photochemistry. By initiating Coulomb explosion through soft X-ray ionization, the authors are able to image ultrafast nuclear dynamics of a prototypical photoreaction.

A hypothetical protein encoded by the gene YajQ of Haemophilus influenzae was selected, as part of a structural genomics project, for X-ray crystallographic structure determination and analysis to assist with the functional assignment. The protein is present in most bacteria, but not in archaea or eukaryotes. The amino acid sequence has no homology to that of other proteins. The YajQ protein was cloned, expressed, and the crystal structure determined at 2.1-A resolution by applying the multiwavelength anomalous dispersion method to a mercury derivative. The polypeptide chain is folded into two domains with identical folding topology. Each domain has a four-stranded antiparallel beta-sheet flanked on one side by two alpha-helices. This structural motif is a characteristic feature of many RNA-binding proteins. The tetrameric structure observed in the crystal suggests a possibility of binding two stretches of double-stranded nucleic acid.

NRC publication: Yes

\"6 With respect to the substantive presentation of evidence, counsel should take on the role of a teacher. Because most judges do not have specialized knowledge of the technical elements of design and construction or scheduling, counsel should find creative ways to educate the judge on these matters so that the judge can efficiently and effectively decide the disputed issues of law and fact. Keep in mind, too, that like arbitrations and dispute review board proceedings, and unlike most jury trials, judges presiding over bench trials tend to become active in the presentation of evidence by, among other things, questioning witnesses directly. [...]in addition to opposing counsel, the judge can pose a threat to an expert's credibility, and an expert witness that is not able to recite with some level of precision the contract's terms and explain how his or her opinion would or would not change if the expert's understanding of the contract ultimately is proved incorrect is much less credible than one who can. [...]the comprehensive \"Construction 101\" required for a jury and judge can be truncated for a sophisticated arbitrator or panel. [...]counsel and the expert should exchange as much information and as many opinions and ideas as possible in order to ensure the expert presents the most thoughtful and focused report.15 With arbitration, counsel can take a far more active role in the drafting of the expert's report than would be desirable for trial.16 In addition, counsel can choose to completely forego the expert's live testimony and submit the report or an affidavit instead.17 This method would really only be selected if the expert is believed to be weak during live testimony.

The protein encoded by the gene ybgI was chosen as a target for a structural genomics project emphasizing the relation of protein structure to function. The structure of the ybgI protein is a toroid composed of six polypeptide chains forming a trimer of dimers. Each polypeptide chain binds two metal ions on the inside of the toroid. The toroidal structure is comparable to that of some proteins that are involved in DNA metabolism. The di-nuclear metal site could imply that the specific function of this protein is as a hydrolase-oxidase enzyme. The quaternary structure taken together with the upgraded response to DNA damage, the inclusion in the operon with endonuclease VIII, and sequential homology with the yeast NIF3 protein appears consistent with a function that involves DNA repair or involvement in the transcription process. Comparison of the active site with known structures has not yet yielded a definitive clue concerning the specific biological function. Biochemical studies to further profile the function of the ybgI protein are in progress.