High-energy X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) of amorphous solid water (ASW) were studied during vapor deposition and the heating process. From the diffraction patterns, the oxygen–oxygen pair distribution functions (PDFs) were calculated up to the eighth coordination shell and an r = 23 Å . The PDF of ASW obtained both during vapor deposition at 80 K as well as the subsequent heating are consistent with that of low-density amorphous ice. The formation and temperature-induced collapse of micropores were observed in the XRD data and in the FTIR measurements, more specifically, in the OH stretch and the dangling mode. Above 140 K, ASW crystallizes into a stacking disordered ice, I sd . It is observed that the fourth, fifth, and sixth peaks in the PDF, corresponding to structural arrangements between 8 and 12 Å, are the most sensitive to the onset of crystallization.
High-density (HDA) and low-density amorphous ices (LDA) are believed to be counterparts of the high- and low-density liquid phases of water, respectively. In order to better understand how the vibrational modes change during the transition between the two solid states, we present infrared spectroscopy measurements, following the change of the decoupled OD-stretch ( v OD ) (∼2460 cm –1 ) and OH-combinational mode ( v OH + v 2 , v OH + 2 v R ) (∼5000 cm –1 ). We observe a redshift from HDA to LDA, accompanied with a drastic decrease of the bandwidth. The hydrogen bonds are stronger in LDA, which is caused by a change in the coordination number and number of water molecules interstitial between the first and second hydration shell. The unusually broad uncoupled OD band also clearly distinguishes HDA from other crystalline high-pressure phases, while the shape and position of the in situ prepared LDA are comparable to those of vapor-deposited amorphous ice.
Amorphous ice plays an important role in our overall understanding of water's phase diagram.
Transarterial chemo‐embolization with drug‐eluting embolic beads (DEB‐TACE) is still evolving. Recent developments include the introduction of radiopaque (X‐ray imageable) drug‐eluting particles. Here, we report on conceptually different radiopaque polymeric drug‐eluting embolic particles, which are (i), cross‐linked poly(methacrylates); (ii), radiopaque; (iii), microporous. Furthermore, the particles are not perfectly spherical: they have a large indentation in the sense that they are either a spherical/cup‐shaped or ellipsoid/mouth‐shaped. The micropores and the large indentation can confer useful features upon the particles, since they can be filled with a crystalline lipophilic chemotherapeutic drug. It is important, in this respect that (i), many potent chemotherapeutics are lipophilic and crystalline; (ii), available drug‐eluting beads (DEBs) have the limitation that they can only be used in combination with water‐soluble chemotherapeutic agents. Cup‐ and mouth‐shaped particles were obtained in a Cu(0) catalyzed free‐radical polymerization reaction. The microparticles could be charged with crystalline drug, in such a manner that the crystals reside in both the micropores and the large cavity, and in quantities that would be required for effective local chemotherapy. The antifungal drug voriconazole, lipophilic, and crystalline, was used to demonstrate this. We believe that the ability of the microporous/cavitated DEBs to carry lipophilic chemotherapeutic drugs is especially important. DEB‐TACE is likely to become a cornerstone method of interventional oncology in the years ahead, and the new embolic particles described herein hold the promise of becoming scope widening for the technique.
Hydrated proteins undergo a transition in the deeply supercooled regime, which is attributed to rapid changes in hydration water and protein structural dynamics. Here, we investigate the nanoscale stress–relaxation in hydrated lysozyme proteins stimulated and probed by X-ray Photon Correlation Spectroscopy (XPCS). This approach allows us to access the nanoscale dynamics in the deeply supercooled regime (T = 180 K), which is typically not accessible through equilibrium methods. The observed stimulated dynamic response is attributed to collective stress–relaxation as the system transitions from a jammed granular state to an elastically driven regime. The relaxation time constants exhibit Arrhenius temperature dependence upon cooling with a minimum in the Kohlrausch–Williams–Watts exponent at T = 227 K. The observed minimum is attributed to an increase in dynamical heterogeneity, which coincides with enhanced fluctuations observed in the two-time correlation functions and a maximum in the dynamic susceptibility quantified by the normalized variance χ T . The amplification of fluctuations is consistent with previous studies of hydrated proteins, which indicate the key role of density and enthalpy fluctuations in hydration water. Our study provides new insights into X-ray stimulated stress–relaxation and the underlying mechanisms behind spatiotemporal fluctuations in biological granular materials.
Hydrated proteins undergo a transition in the deeply supercooled regime, which is attributed to rapid changes in hydration water and protein structural dynamics. Here, we investigate the nanoscale stress relaxation in hydrated lysozyme proteins stimulated and probed by X-ray Photon Correlation Spectroscopy (XPCS). This approach allows us to access the nanoscale dynamic response in the deeply supercooled regime (T = 180 K) which is typically not accessible through equilibrium methods. The relaxation time constants exhibit Arrhenius temperature dependence upon cooling with a minimum in the Kohlrausch-Williams-Watts exponent at T = 227 K. The observed minimum is attributed to an increase in dynamical heterogeneity, which coincides with enhanced fluctuations observed in the two-time correlation functions and a maximum in the dynamic susceptibility quantified by the normalised variance χ T . Our study provides new insights into X-ray stimulated stress relaxation and the underlying mechanisms behind spatiotemporal fluctuations in biological granular materials.
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