Two elastin-like poly(pentapeptides), poly(AV1GV2P) and poly(G1V1G2V2P), have been studied in water and in solid state by ATR FTIR and Raman spectroscopy in combination with model ab initio calculations. In aqueous solutions below the transition temperature T(t), a part of the amide groups and of the methyl groups of both polypentapeptides interacts with neighboring water molecules, whereas the other part of amide groups mutually interacts forming a beta-sheetlike structure. Below T(t), poly(AV1GV2P) is dissolved more perfectly, and the water shells around the polymer chains are more closely structured. The suspension of poly(AV1GV2P) formed above T(t) is more compact and, on cooling, resists more to the reverse dissolution, whereas the suspension of poly(G1V1G2V2P) contains more water molecules bound to the carbonyl of amide groups and on backward cooling dissolves fairly reversibly. The measured poly(pentapeptides) tend to form beta-turns due to the conformational transition on the residue between P and V1.

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The structure and dynamics of two synthetic elastin-like polypentapeptides, poly(G(1)V(1)G(2)V(2)P) and poly(AV(1)GV(2)P), were studied in D(2)O and H(2)O at various temperatures by using (1)H, (2)H,(13)C, and (15)N NMR spectra, relaxations, and PGSE self-diffusivity measurement. Signal assignments were made using COSY, NOESY, HXCORR, HSQC, HMBC, and SSLR INEPT techniques. Temperature-induced conformation changes were studied using (3)J(NHCH) couplings, NOESY connectivity, chemical shifts, and signal intensities. Hydrodynamic radii were derived from self-diffusion coefficients measured by the pulsed-gradient spin-echo (PGSE) method. Selective hydration (hydrophilic or hydrophobic) was explored using NOESY and ROESY spectral methods and longitudinal and transverse (1)H relaxation of HOD and quadrupolar (2)H relaxation of D(2)O. Four different physical states were discerned in different temperature regions for both polymers: state I of a rather extended, statistically shaped and fully hydrated polymer below the critical temperature (approximately 299-300 K); state II, a relatively coiled and globular but disordered preaggregation state, developing in a rather narrow region, 300-303 K, in the case of poly(AV(1)GV(2)P) and in a broader region, overlapping with the next one, in poly(G(1)V(1)G(2)V(2)P); state III, a tightly coiled, more compact state in the region 303-313 K; and, finally, state IV, an aggregated (and eventually flocculating and sedimenting) state beyond 313 K. States II-IV coexist in varying proportions in the whole temperature range above 299 K. A structure characterized by a beta-turn stabilized by H-bonding between the Ala carbonyl and Val(2) NH groups of poly(AV(1)GV(2)P) was detected by NOESY just above the transition temperature. States II and III are progressively more stripped of their hydration sheath but retain some molecules of water confined and relatively immobilized in their coils.