Abstract. Gabapentin, C9H17NO2, 2-[1-(aminomethyl)cyclohexyl]acetic acid, is used as an anticonvulsant drug to help control partial seizures in the treatment of epilepsy and to manage postherpetic neuralgia after 'shingles'. Cocrystals of gabapentin with a series of hydroxyl carboxylic acids and a cocrystal of gabapentin with oxalic acid were previously reported. The adduct with salicylic acid was prepared, along with adducts of two dicarboxylic acids, succinic acid and adipic acid, and an adduct with 1,2,4,5-benzenetetracarboxylic acid. Formation of new materials is demonstrated by new unique physical properties, including lower melting points (102.8-105.1 ºC, 90.0-93.0 ºC, and 152.4-154.8 ºC for succinic acid, adipic acid, and 1,2,4,5-benzenetetracarboxylic acid products, respectively) than those of the individual starting materials. Shifts in infrared bands for ν (O-H), ν(N-H), and ν(C=O) bands confirm adduct formation and indicate the nature of the interactions between the two components in the lattice.
Lead phosphate crystals were grown in agarose gel at room temperature. Nucleation and crystal growth rates were controlled by changing the density of the gel medium including pure and phosphate gel. Individual crystallites from the pure gel layer show equant habit while those from the PO4 3− gel layer show plate-like habit. Vibrational spectra indicate that the PO4 3-ion is distorted and its symmetry is lower than free ion symmetry. Powder diffraction patterns of the pure gel products show mixed phases of PbHPO4, Pb3(PO4)2, and Pb5(PO4)3OH (PbHAp) consistent with saturation index predictions obtained from the PHREEQC program. Formation of the microscopic crystalline products was accompanied by a decrease in pH from 8 (theoretical for all layers mixed) to 3 for all reactions studied, consistent with PbHPO4 being the major product. PbHAp does not appear in the phosphate gel layer because of the higher Pb:P ratio required for the PbHAp phase relative to the Pb3(PO4)2 phase. PbHAp crystals from the gel crystallization method are first reported in this work as microcrystalline product deposited on the surface of the dominant phase formed in the pure gel layer.
Poster Sessions C281[1], [2].A sequence of bidimensional X-ray diffraction patterns were acquired in transmission mode at regular intervals across the shell thickness. The scattering or degree of preferential orientation of crystals was calculated from the intensity profile along the selected Debye-Scherrer rings (χ-scans).The degree of crystal orientation was determined from the angular length of the arcs displayed in the Debye rings on the 2D X-ray diffraction patterns. The values of reflection intensities, degree of orientation and crystallinity show progressive variations within during the same shell layer as well as abrupt changes at the transitions between layers with different microstructural organizations. This study provides useful insights into both the mechanisms that control the development of order in mollusc shell microstructures and those that determine the switch between layers with different microstructural organizations.This information could be of interest to understand the processes of self-assembly that happen in these biomaterials and may be applied to the design of bio-inspired advanced ceramic materials. The nucleation of hemozoin (HZ) in the digestive vacuole (DV) of Plasmodium falciparum in malaria-infected red blood cells (RBCs) is a topic of current interest. HZ crystals have been reported encased within neutral lipid nanospheres in the DV, which appears inconsistent with the concepts of catalyzed nucleation of HZ at a lipid surface and inhibition of nucleation of HZ via antimalarials that target the HZ crystal surface. To resolve this conundrum, we probed the orientation of HZ crystals in the DV, their position, the site and mechanism of nucleation. HZ crystal clusters in the RBCs were detected and their amount estimated by microfocus X-ray Fe-fluorescence, and their orientations determined by microfocus X-ray diffraction. The diffraction patterns were interpreted in terms of HZ crystals aligned along their needle axes, arranged on a curved surface, exposing their {100} side faces. Using various microscopy techniques, including stain-free cryogenic soft X-ray tomography, freeze-fracture SEM and thin section TEM, we find that nucleation occurs in proximity to the DV inner membrane, where furthermore we find a thickened lipid coating. Morphological evidence supports the {100} orientation facing the lipid, consistent with interpretation of X-ray diffraction results (mentioned above) and in vitro nucleation of synthetic hemozoin at various interfaces. Calcium hydroxyapatite (CaHAP, Ca 5 (PO 4 ) 3 (OH)) is the dominant component of human enamel, dentin, and bone. Its structure belongs to space group P6 3 /m and is susceptible to ionic substitution in both anion and cation sites. Pb 2+ can replace Ca 2+ in the apatite structure resulting in lead hydroxyapatite (PbHAP) which is isostructural with CaHAP. This work reports products from a gel crystallization method used for preparation of larger crystals of PbHAP by controlling nucleation and crystal growth rate by changing the density of th...
Calcium hydroxyapatite, CaHAp, synthesized by the precipitation method, was utilized to study the calcium-lead metathesis reaction on dissolution in a lead nitrate solution under reflux conditions to prepare larger lead hydroxyapatite, PbHAp, crystals from CaHAp. SEM images show development of crystalline PbHAp on the surfaces of CaHAp. The needle-like crystal morphology observed for PbHAp after 24 h reaction time developed into hexagonal-rod crystal morphology within 48 h reaction time. The largest PbHAp crystals obtained from 48 h reaction time have approximate size of 10 × 10 × 40 μm. Powder X-ray diffraction results show mixed phases of CaHAp and PbHAp due to difficulty in separating the PbHAp product from the CaHAp substrate. The PbHAp peaks observed after 24 h of reaction sharpen and increase in intensity after 48 h of reaction confirming that the PbHAp phase is the major product for the 48 h reaction time. EDX results of the crystalline products show high intensity Pb peaks with lead to phosphorous ratio (5 : 3) as expected for PbHAp. Lower intensity Ca peaks are also observed, consistent with incomplete coverage of the CaHAp growth substrate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.