Roles of Electrostatics and Conformation in Protein-Crystal Interactions

In vitro studies have shown that the phosphoprotein osteopontin (OPN) inhibits the nucleation and growth of hydroxyapatite (HA) and other biominerals. In vivo, OPN is believed to prevent the calcification of soft tissues. However, the nature of the interaction between OPN and HA is not understood. In the computational part of the present study, we used molecular dynamics simulations to predict the adsorption of 19 peptides, each 16 amino acids long and collectively covering the entire sequence of OPN, to the {100} face of HA. This analysis showed that there is an inverse relationship between predicted strength of adsorption and peptide isoelectric point (P<0.0001). Analysis of the OPN sequence by PONDR (Predictor of Naturally Disordered Regions) indicated that OPN sequences predicted to adsorb well to HA are highly disordered. In the experimental part of the study, we synthesized phosphorylated and non-phosphorylated peptides corresponding to OPN sequences 65–80 (pSHDHMDDDDDDDDDGD) and 220–235 (pSHEpSTEQSDAIDpSAEK). In agreement with the PONDR analysis, these were shown by circular dichroism spectroscopy to be largely disordered. A constant-composition/seeded growth assay was used to assess the HA-inhibiting potencies of the synthetic peptides. The phosphorylated versions of OPN65-80 (IC50 = 1.93 µg/ml) and OPN220-235 (IC50 = 1.48 µg/ml) are potent inhibitors of HA growth, as is the nonphosphorylated version of OPN65-80 (IC50 = 2.97 µg/ml); the nonphosphorylated version of OPN220-235 has no measurable inhibitory activity. These findings suggest that the adsorption of acidic proteins to Ca2+-rich crystal faces of biominerals is governed by electrostatics and is facilitated by conformational flexibility of the polypeptide chain

High neutrophil to lymphocyte ratio and decreased CD69+NK cells represent a phenotype of high risk in early-stage breast cancer patients

Pablo Mand&oacute;,1,* Manglio Rizzo,2,* Mar&iacute;a Paula Roberti,1 Estefan&iacute;a Paula Juli&aacute;,1 Mar&iacute;a Betina Pampena,1 Constanza P&eacute;rez de la Puente,2 Carlos Mart&iacute;n Loza,2 Carolina Ponce,2 Jorge Nadal,2 Federico Andres Col&oacute;,2 Jos&eacute; Mordoh,1&ndash;3 Estrella Mariel Levy1 1Oncology Research Center CIO-FUCA, Buenos Aires, Argentina; 2Alexander Fleming Institute, Buenos Aires, Argentina; 3Biochemical Research Institute of Buenos Aires, Buenos Aires, Argentina *These authors contributed equally to&nbsp;this work Purpose: Breast cancer (BC) is a highly heterogeneous disease presenting a broad range of clinical and molecular characteristics. In the past years, a growing body of evidence demonstrated that immune response plays a significant role in cancer outcome. However, immune prognostic markers are not completely validated in clinical practice in BC patients. Materials and methods: With the aim to characterize immune features, several parameters were analyzed in peripheral blood at diagnosis of 85 nonmetastatic BC patients between April 2011 and July 2014. Results: With a median follow-up of 38.6 months, peripheral blood analysis of BC patients (stages I, II, and III) showed that total lymphocyte and T lymphocyte counts were augmented in nonrelapsed patients. Also, a higher neutrophil-to-lymphocytes ratio was associated with prolonged disease-free survival. Natural killer cell receptor analysis revealed that early activation receptor CD69 was associated with a better outcome. Conclusion: This preliminary evidence is in accordance with the concept of immune surveillance. We suggest an &ldquo;immune phenotype&rdquo; that provides relevant prognostic information in early-stage BC patients and which could be useful in the decision-making process. Keywords: breast neoplasm, prognostic factors, lymphocytes, neutrophil-to-lymphocyte rati