Phase transition of L‐Ser monohydrate crystal studied by ¹³C solid‐state NMR

Abstract

We used gravimetric analysis (GA) and (13)C solid-state nuclear magnetic resonance (NMR) to study solid-phase transition from the transparent single crystal of L-serine (L-Ser) monohydrate to a turbid powder. We found that L-Ser monohydrate loses water molecules and transforms into an anhydrate, thus experimentally demonstrating Frey's assumption. Application of a handmade cross-polarization (CP) NMR probe with a saddle-type coil to the oriented crystal of the L-Ser monohydrate revealed the dehydration mechanism. Furthermore, the chemical shift tensor components of the carboxyl carbon in L-Ser monohydrate were determined. The difference in the tensor component of delta(22) between the monohydrate and anhydrate forms was more than 7 ppm, probably owing to differences in the hydrogen-bonding structure of each form.

Physicochemical properties of surface charge-modified ZnO nanoparticles with different particle sizes

“…29 On the other hand, the nuclear magnetic resonance spectra for the L-serine-coated ZnO samples showed peaks at 63.2 ppm and 56.1 ppm, corresponding to the C β and C α carbons in the amino acids. 28 These results again confirmed that the C, O, and N peaks in XPS were attributable to the coating agents and dispersants.…”

“…All four types of coated ZnO nanoparticles showed δ 11 (COO -) and δ 22 (COO -) peaks, and these were attributed to the carboxylates in citrate and L-serine. 27,28 In the citrate-coated ZnO nanoparticles, the characteristic peak of the quaternary 30 40 2θ ( carbon (C q ) of citrate was found at 76.6 ppm, and C 1 , C 2 , C 3 , C 4 , and C 5 peaks originating from HEPES were observed in the range of 50-60 ppm ( Figure 4A-C). 29 On the other hand, the nuclear magnetic resonance spectra for the L-serine-coated ZnO samples showed peaks at 63.2 ppm and 56.1 ppm, corresponding to the C β and C α carbons in the amino acids.…”

Structure and Thermal Analyses of MAA‐Grafted Silk Fiber Using DSC and 13C Solid‐State NMR

“…Grafting was originally introduced as an alternative to the traditional mineral weighting technique (tin-phosphate-silicate weighting), a method used for decades to increase silk weight in order to compensate for the loss resulting from degumming. [3] However, in recent years grafting has been regarded not only as an effective treatment for increasing silk weight but also as a powerful Summary: By using DSC, 13 C CP/MAS NMR and SEM, we studied the physical properties and chemical structure of silk fibers grafted with methacrylamide (MAA). At a given MAA concentration, the inverse of fiber weight gain linearly increased with increasing square root of the initiator concentration, and at a given initiator concentration the fiber weight gain increased with increasing MAA concentration.…”

“…At a given MAA concentration, the inverse of fiber weight gain linearly increased with increasing square root of the initiator concentration, and at a given initiator concentration the fiber weight gain increased with increasing MAA concentration. 13 C CP/ MAS NMR demonstrated that the primary and secondary structure remained unchanged, regardless of MAA grafting, implying the poor compatibility and the lack of new additional hydrogen bonding between the silk fiber and the MAA graft polymer. The degree of grafting in MAA-grafted silk fiber (the accurate amount of actually loaded MAA polymer within the fiber matrix) can be evaluated from determination of the ratio of heat capacities calculated from two individual endothermic DSC peaks of silk fibroin and MAA polymer.…”

“…Solid-state NMR spectroscopy is an effective tool for the characterization of mixed systems that are difficult to analyze by diffraction methods such as X-ray diffraction. [10][11][12][13] Therefore, solidstate NMR can be applied to the structural analysis of silk fiber grafted with polymers. Although many structural studies of silk have been carried out by using solid-state NMR, [14][15][16][17][18] to our knowledge no study has reported the use of NMR parameters to elucidate the structure of silk fibers grafted with vinyl monomers.…”