The structural dynamics of two elastically bendable, halogenated N-benzylideneaniline organic crystals were studied using an in situ three-point bending test and Raman spectroscopy. This study reveals the inhomogeneous molecular distribution in the elastic crystal lattice during the bent stage and further validates the known qualitative mechanistic model of elastic bendable crystals.

Insights into structure–mechanical property correlations in molecular and multicomponent crystals have recently attracted significant attention owing to their practical applications in the pharmaceutical and specialty fine chemicals manufacturing. In this contribution, we systematically examine the mechanical properties of dimorphic forms, Forms I and II, of a 1:1 caffeine–glutaric acid cocrystal on multiple faces using nanoindentation to fully understand their mechanical anisotropy and mechanical stability under an applied load. The higher hardness, H, and elastic modulus, E, of stable Form II has been rationalized based on its corrugated layers, higher interlayer energy, lower interlayer separation, and presence of more intermolecular interactions in the crystal structure compared to metastable Form I. Our results show that mechanical anisotropy in both polymorphs arises due to the difference in orientation of the same two-dimensional structural features, namely, the number of possible slip systems, and the strength of the intermolecular interactions with respect to the indentation direction. The mechanical properties results suggest that the 1:1 caffeine–glutaric acid cocrystal, metastable form (Form I) could be a suitable candidate with desired tablet performance to that of stable Form II. Overall, it demonstrates that the multiple faces of nanoindentation are critical to determine mechanical anisotropy and structure-mechanical property correlations. Further, the structural–mechanical property correlations aid in the selection of the best solid phase for macroscopic pharmaceutical formulation.

In this article, we have studied the binding of different naturally occurring hemoglobin (Hb) variants on erythrocyte skeletal protein, spectrin surface using the label free nondestructive second harmonic light scattering (SHLS) technique in aqueous buffer. Hemoglobin variants like sickle hemoglobin (HbS) and hemoglobin E (HbE) were chosen as they associate with sickle cell disease and HbEβ-thalassemia, respectively, and their interaction with spectrin is compared with normal adult hemoglobin (HbA). The concentration dependent change in the second harmonic light intensity from nanomolar spectrin solution has been measured after addition of small aliquots of hemoglobins. From the second harmonic titration data, the binding constant is calculated using a modified Langmuir adsorption model of hemoglobin binding to the spectrin surface. Interestingly, it is found that the binding constant for HbE (13.8 × 10 M) is 1 order of magnitude higher than that of HbS (1.6 × 10 M) or HbA (2.1 × 10 M) which indicates higher affinity of HbE for spectrin compared to HbA and HbS. The number of the Hb molecules bound to the spectrin surface was estimated to be of the order of hundred's which is determined for the first time.

Lysozyme adsorption on gold nanoparticles is an enthalpically driven process while the entropy contribution is favourable but insignificant.

Characterization of nanoparticle protein corona has gained tremendous importance lately. The parameters which quantitatively establish a specific nanoparticle-protein interaction need to be measured accurately since good quality data is necessary...