Melting properties of peptides and their solubility in water. Part 1: dipeptides based on glycine or alanine

Abstract

Combination of the PC-SAFT and FSC methods allows for accurate prediction of dipeptide solubility in water in a wide temperature range without the need to fit any model parameters to experimental solubility data.

Experimental solubility and density studies on aqueous solutions of quaternary ammonium halides, and thermodynamic modelling for melting enthalpy estimations

“…To the best of our knowledge this calorimetric technique has not yet been applied for salts, and no reliable melting enthalpy data are available for the alkylammonium salts studied in this work. Similarly to the work of Do et al [81], the very good correlation results achieved in this work using PC-SAFT for the description of water activity coefficients, aqueous salt solution densities and solubility of the salt in water suggests the use of the PC-SAFT model to estimate the melting enthalpies of the studied salts. The values found are probably the best estimates to perform solid-liquid equilibrium studies, which are of utmost importance when designing and screening new (deep) eutectic mixtures.…”

“…In fact, the measurement of the melting properties of pure substances that decompose upon melting is quite difficult to perform, but very recently fast scanning calorimetry has been showing to be a promising technique. This has been primarily tested for low-molecular weight organic compounds [80] and very recently also tested to measure the melting properties of small peptides [81]. In this last work the activity and osmotic coefficients as well as densities in aqueous solutions were used to estimate PC-SAFT parameters, which were after combined with the measure melting properties to predict the solubility of the peptides in water showing very good agreement with the experimental observations.…”

Melting properties of amino acids and their solubility in water

“…22,23 The experimental FSC study of the AA was given in the previous works, where detailed experimental description of FSC method has been presented. 14,24 All measurements were conducted under inert atmospheres of dry nitrogen (dew point lower than 150 K) with a ow rate of 50 mL min À1 . The sensors were conditioned according to manufacturer's procedure and the temperature was calibrated with recommended calibration metals (indium, bismuth and tin).…”

“…] is the total heat capacity of the sample from the rst FSC stage and c S p0i [J mol À1 K À1 ] is specic heat capacity obtained DSC measurements (Pyris 1, Perki-nElmer, USA). 14,16,19,[24][25][26] In the second stage, the melting properties were determined in heating step #5. To improve the thermal contact between the sample and the sensor, silicon oil can be added to the sample before heating step #5.…”

“…This allows indirect determination of Dc SL p0i (T G 0i ) at glass transition temperature and adjustment to melting temperature, Dc SL p0i (T SL 0i ), which is required in eqn (1). 24 In Fig. 1(b), the melting temperature was determined by extrapolating the onset melting temperature at different scanning rates to zero scanning rate b, DT SL 0i (b / 0), considering the thermal lag and possible superheating.…”