Conformational characterization of Bombyx mori silk fibroin in the solid state by high-frequency carbon-13 cross polarization-magic angle spinning NMR, x-ray diffraction, and infrared spectroscopy

1985 ◽  
Vol 18 (10) ◽  
pp. 1841-1845 ◽  
Author(s):  
Tetsuo Asakura ◽  
Akio Kuzuhara ◽  
Ryoko Tabeta ◽  
Hazime Saito
Keyword(s):  
Infrared Spectroscopy ◽  
High Frequency ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Cross Polarization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bombyx Mori Silk ◽  
Angle Spinning

Synthesis and characterization of montmorillonite-type phyllosilicates in a fluoride medium

Clay Minerals ◽  
2005 ◽  
Vol 40 (2) ◽  
pp. 177-190 ◽  
Author(s):  
M. Reinholdt ◽  
J. Miehé-Brendlé ◽  
L. Delmotte ◽  
R. Le Dred ◽  
M.-H. Tuilier
Keyword(s):  
Atomic Ratio ◽  
Magic Angle Spinning ◽  
Crystallization Time ◽  
Magic Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Angle Spinning ◽  
Mg Content ◽  
Fluoride Medium

AbstractThe fluorine route is thoroughly investigated for the hydrothermal synthesis of montmorillonite in the Na2O-MgO-Al2O3-SiO2-H2O system. Using the optimal conditions suggested by Reinholdt et al. (2001) for the crystallization of pure montmorillonites with the formula Na2x(Al2(1-x)Mg2x☐)Si4O10(OH)2, several parameters (x, Mg content, duration of crystallization, F/Si atomic ratio, pH, nature of counterbalance cation) are varied independently from their ideal values. The products are analysed by various techniques (X-ray diffraction, thermogravimetric analysis-differential thermal analysis, 29Si, 27Al and 19F magic angle spinning-nuclear magnetic resonance). It appears that a pure montmorillonite can only be obtained within a narrow x range (0.10 ≤ x ≤ 0.20). The presence of F in the starting hydrogel and the crystallization time also have significant effects on the purity of the final products. It is shown that a small amount of fluorine is needed for the crystallization of pure montmorillonite phyllosilicates.

Lewis-Base Adducts of Group I Metal(I) Compounds. XXVI. Solid-State Cross-Polarization Magic-Angle-Spinning 31P N.M.R. and Structural Studies on 1:1 Adducts of Triphenylphosphine With Gold(I) Salts

1987 ◽  
Vol 40 (9) ◽  
pp. 1545 ◽  
Author(s):  
PF Barron ◽  
LM Engelhardt ◽  
PC Healy ◽  
J Oddy ◽  
AH White
Keyword(s):  
Solid State ◽  
Magic Angle Spinning ◽  
Lewis Base ◽  
Magic Angle ◽  
Molecular Formula ◽  
Cross Polarization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Group I ◽  
Angle Spinning

Linear, two-coordinate compounds of molecular formula (PPh3) AuX have been characterized by solid-state and solution 31P n.m.r. spectroscopy, and single-crystal X-ray diffraction techniques. The solid state n.m.r. spectra reveal single, broad resonance lines for X = NO3 (chemical shift 19 ppm , ref. 85% H3PO4), CH3C02 (24 ppm), SCN (36ppm), CN (37 ppm ) and CH3 (47 ppm ) and doublets for X = Cl (27, 33 ppm ), Br (28, 36 ppm ) and I (34, 38 ppm ), the latter three spectra being recorded at 121.47 MHz and 161.96 MHz. Solution spectra show relatively sharp single resonances for each compound with 6 values generally slightly higher than in the solid state. Crystal data are reported for X = NO3, space gro )p P21/c, a 8 895(9), b 10.117(8), c 19.57(2) �; β 97.43(8)�, Au-P,O = 2.199(5), 2.02(1) �. Crystals of compounds with X = Br, I and SCN are isomorphous with the AuCl compound, belonging to space group 212121. For X = Br, a 12.479(5), b 13.45(1), c 10.0!2(8) �; Au-P, Br = 2.252(6), 2.407(2) �. For X = I, a 12.529(8), b 13.870(5), c 10.188(4) �; Au-P, I = 2.254(5), 2.556(2) �. For X = SCN, a 12.257(5), b 13.776(8), c 10.754(6) �; Au-P, S = 2.252(7), 2.304(7) �.

scholarly journals Conversion of sub-µm calcium carbonate (calcite) particles to hollow hydroxyapatite agglomerates in K2HPO4 solutions

2020 ◽  
Vol 9 (1) ◽  
pp. 945-960
Author(s):  
Sun Yanyan ◽  
Wang Guangxin ◽  
Li Wuhui ◽  
Wang Yaming ◽  
Satoshi Hayakawa ◽  
...  
Keyword(s):  
Activation Energy ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Cross Polarization ◽  
X Ray Diffraction ◽  
Nmr Studies ◽  
X Ray ◽  
Order Of Magnitude ◽  
Angle Spinning ◽  
Cp Mas Nmr

AbstractSub-µm CaCO3 (calcite; CC) particles were converted to calcium monohydrogenphosphate dihydrate (DCPD) and hydroxyapatite (HAp) via soaking treatments in K2HPO4 solutions with varied pH (3–12) and concentrations (0.1–1.5 M) at 37°C for up to 10 days. DCPD was derived from the solutions with pH ≤ 6; while hollow HAp was yielded when pH ≥ 7 in assemblies of petal-like crystallites. Results of magic angle spinning (MAS) and cross-polarization magic angle spinning (CP-MAS) NMR studies have shown that the HAp lattice has only PO42− but no HPO42− at B (phosphate) sites. Trace amounts of CO32− have occupied both A (OH) and B (PO4) sites, and H2O is adsorbed on surface crystallites. The primary crystallite size of HAp derived from Scherrer equation increases quickly in a 12 h period and becomes gradually stable afterward. Samples of particles soaked within 3 h in a temperature range of 20–80°C were analyzed by X-ray diffraction. It is shown that the rate constant of 1 M solution is about an order of magnitude greater than that of 0.1 M solution and the apparent activation energy is 33 kJ/mol. In this work, the conversion of CC to HAp can be quantitatively controlled to solve the problem of slow degradation of HAp.

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