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Mineral-associated proteins have been proposed to regulate many aspects of biomineralization, including the location, type, orientation, shape, and texture of crystals. To understand how proteins achieve this exquisite level of control, we are studying the interaction between the phosphoprotein osteopontin (OPN) and the biomineral calcium oxalate monohydrate (COM). In the present study, we have synthesized peptides corresponding to amino acids 220-235 of rat bone OPN (pSHEpSTEQSDAIDpSAEK), one of several highly phosphorylated, aspartic-, and glutamic acid-rich sequences found in the protein. To investigate the role of phosphorylation in interaction with crystals, peptides containing no (P0), one (P1), or all three (P3) phosphates were prepared. Using a novel combination of confocal microscopy and scanning electron microscopy, we show that these peptides adsorb preferentially to {100} faces of COM and inhibit growth of these faces in a phosphorylation-dependent manner. To characterize the mechanism of adsorption of OPN peptides to COM, we have performed the first atomic-scale molecular-dynamics simulation of a protein-crystal interaction. P3 adsorbs to the {100} face much more rapidly than P1, which in turn adsorbs more rapidly than P0. In all cases, aspartic and glutamic acid, not phosphoserine, are the amino acids in closest contact with the crystal surface. These studies have identified a COM face-specific adsorption motif in OPN and delineated separate roles for carboxylate and phosphate groups in inhibition of crystal growth by mineral-associated phosphoproteins. We propose that the formation of close-range, stable, and face-specific interactions is a key factor in the ability of phosphoproteins to regulate biomineralization processes. [ABSTRACT FROM AUTHOR]

At the beginning of the 21st century the hypopharynx and the cervical esophagus cancer represents a major issue for all countries of the world. The epidemiology of the hypopharynx and cervical esophagus cancer deals with the spread of the disease in the human population with regard to sex, age, profession, time and space, as well as risk factors that contribute to these phenomena. The main goal is to investigate the causes and the factors involved in the development of the tumors at the pharyngoesophageal junction, knowledge that contributes to the latest therapeutic assessment through interdisciplinary collaboration (E.N.T. surgeon, general surgeon, radiation oncologist, chemotherapist, and nutritionist). The epidemiology of the hypopharynx and cervical esophagus cancer includes three major areas of interest: descriptive (the study of the spread in mass population), analytical (the study of causal risk factors on the disease) and experimental (that verifies by experiments on animals the prior identified hypothesis).