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Raman data collected from free amino acid and peptide chains permit assignment of the seven markers located at approximately 1616, 1606, 1210, 1178, 850, 830, and 643 cm−1 to tyrosine. The effects induced by labile hydrogen deuteration, temperature, concentration, and protonation–deprotonation on these Raman markers were analyzed. Following closely a recent multiconformational analysis on phenylalanine, we could confirm the predominance of gauche-/gauche- rotamers with respect to the side chain χ1/χ2 torsion angles in both tyrosine and tyrosinate. Calculated Raman spectra, based on the consideration of both implicit and explicit hydration models, have revealed the effect of hydrogen bonding of water molecules to the phenol ring hydroxyl group of tyrosine. A special attention has been paid to the 850/830 cm−1 tyrosine doublet, for which no intensity ratio inversion could be remarked when the phenol hydroxyl group acts as a hydrogen bond donor or acceptor. On the contrary, this intensity ratio appeared to be strongly dependent on the hydrophobic/hydrophilic balance of the interactions, in which the phenol ring is involved. Based on the present theoretical calculations, the components of the tyrosine doublet might originate from two independent fundamental modes of the phenol ring: one with an in-plane character and the other with an out-of-plane character. As a consequence, the widely spread Fermi resonance-based description of the tyrosine doublet appears to be unjustified. The latter interpretation simply results from the insufficiencies of the simple model compound used at that time for analyzing the vibrational features of a more complex molecular system such as tyrosine. Copyright © 2015 John Wiley & Sons, Ltd.

This work was granted access to the HPC resources of CINES (Montpellier, France) under the allocations c2013075065 and c2014085065 made by GENCI (Grand Equipement National de Calcul Intensif). The authors would like to acknowledge CSIC for the Project I-LINK 0646 facilitating the collaboration between the Spanish and French groups.

Thanks to a considerable modulation of electronic polarizability, six phenylalanine (Phe) vibration modes located at ca. 1606, 1586, 1207, 1031, 1004 and 622 cm−1 appear as intense or medium bands in the Raman spectra of peptides and proteins, as confirmed by the Raman data collected from free amino acid, somatostatin and bovine serum albumin (BSA). To get information on the nature and location of these lines, we resorted to a multiconformational analysis which consists in a systematic investigation of the structural and vibrational features of hydrated Phe in a conformational space depending on four angular variables: φ, ψ, χ1 and χ2. The first two variables correspond to the Phe backbone torsion angles, whereas the latter two refer to its side chain. Based on a protocol described in an accompanying report on glycine and its protonated and deprotonated species, we have prepared an initial set of 123 initial clusters of Phe + 5H2O, including all plausible values of the above mentioned conformational angles. The results of their geometry optimization, by means of the density functional theory using the B3LYP hybrid functional, were first analyzed through the comparison between the E(χ1, χ2) energy maps obtained either by an explicit or by an implicit hydration model. Then, a set of nine doubly minimized clusters corresponding to the deepest local minima were used for further structural and vibrational analysis. Beyond providing a reliable assignment for the above mentioned characteristic Raman lines, the theoretical spectrum allowed us to carry out an overview of the whole observed data of Phe in aqueous solution. Copyright © 2013 John Wiley & Sons, Ltd.

The kinetic study of copolymers synthesis is important to understand how a material is built and how it can get some particular properties. The radical copolymerization of one, two or more monomers can be simulated with classical analytic models, but can also be simulated by a Monte Carlo model that allows a bigger flexibility and is a lot easier to compute and use. We have shown that this Monte Carlo simulation gives the same results of the kinetic stud of the terpolymerization as the analytic model, and it can create easily a bank of virtual copolymers for all the compositions needed to analyze the structure of the macromolecular chains in term of sequence of monomers occurring as a function of the global composition. The search for the sequences is very simple to compute as it consists in a simple reading of the virtual chains previously simulated. This result can thus be applied to make appear a simple correlation between the distribution of functional groups and some specific observed biological activities of biospecilic copolymers.

Previous results obtained have shown that it was possible to create biospecific sites onto polymers through statistic modifications of polystyrene derivatives copolymer with given chemical groups or through synthesis of random methacry late-based copolymers. Such polymers show biological activities (anticoagulant, cell proliferation modulation...) dependent of the global composition and thus of the statistical distribution of the functional groups, and the number of biospecific sites is simply correlated to the observed biological activity. The study of the radical terpolymerization allow us to use a Monte Carlo based synthesis simulation and to determine the occurrence frequency of three to twenty monomers sequence as a function of the conversion rate and the global composition. The comparison of the sequences occurrence curves as a function of the global composition of the polymers with the experimental cell proliferation inhibition curve led us to extract a series of eight monomers sequence with similar structure properties representing a group of biospecific sites responsible for the observed biological activity.