Enhanced the Negative Charges of Antheraea pernyi Silk Fibroin by Methylglyoxal Modification

2015 ◽  
Vol 1101 ◽  
pp. 307-313 ◽  
Author(s):  
Jing Li ◽  
Ceng Zhang ◽  
Yi Zhang ◽  
Yan Ni Yu ◽  
Jing Wan Luo ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Silk Fibroin ◽  
Nmr Spectra ◽  
Negative Charge ◽  
Controlled Drug Release ◽  
Side Chain ◽  
Antheraea Pernyi ◽  
H Nmr ◽  
Chemically Modified ◽  
Positively Charged

Antheraea pernyi silk fibroin has favorable biocompatibility, good bioactivity and controllable biodegradability, meeting the basic requirements of controlled drug release carriers. Enhancing the negative charge of silk fibroin could further increase the encapsulation and loading efficiency of positively charged drugs. In this study, Antheraea pernyi silk fibroin was chemically modified by methylglyoxal in aqueous solution. The electric charge properties of Antheraea pernyi silk fibroin were examined to characterize the modification, the results indicated that the isoelectric point of Antheraea pernyi silk fibroin decreased from 4.5 to 3.9, and the zeta potential reduced from-11.7 mV to-12.8 mV. Amino acid analysis and 1H-NMR spectra showed that arginine residue of Antheraea pernyi silk fibroin side chain was modified by methylglyoxal for enhancing negative charge of silk fibroin. These results suggested that methylglyoxal-modified Antheraea pernyi silk fibroin could be considered as a potential starting material in loading positively charged drugs.

sHigh resolution 1H nuclear magnetic resonance studies of a flavine and its product with MoCl4

1977 ◽  
Vol 55 (4) ◽  
pp. 575-582 ◽  
Author(s):  
T. Roberie ◽  
N. S. Bhacca ◽  
J. Selbin
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Binding Sites ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Side Chain ◽  
Magnetic Resonance Studies ◽  
H Nmr ◽  
Metal Atoms ◽  
1H Nuclear Magnetic Resonance

The high resolution 1H nmr spectra of the substituted flavine, 3-N-methyltetraacetylriboflavine (3-Me-TARF), and its non-aqueous solution complexes with Gd(fod)3, Eu(fod)3, MoCl4, and MoCl4•2CH3(CH2)2CN, were studied in order to try to discern the binding sites of the flavine as it attaches to the molybdenum. Evidence was found that all three metal atoms, Gd(III), Eu(III), and Mo(IV), are attached in solution not only by the primary binding (chelating) sites of the flavine, viz., the O-4 and N-5 atoms, but also by an acetyl oxygen atom, at the C-4′ site of the ribityl side chain. 300 MHz spectra of the 3-Me-TARF have permitted the coupling constants for the side chain methine and methylene protons to be obtained.

E-Homolupane Derivatives Substituted in Position 17 and 22a. 1H NMR, 13C NMR and IR Spectra

1995 ◽  
Vol 60 (4) ◽  
pp. 619-635 ◽  
Author(s):  
Václav Křeček ◽  
Stanislav Hilgard ◽  
Miloš Buděšínský ◽  
Alois Vystrčil
Keyword(s):  
Nmr Spectra ◽  
2D Nmr ◽  
Coupling Constants ◽  
Side Chain ◽  
Oxidation Reactions ◽  
H Nmr ◽  
Complete Assignment ◽  
Nmr Techniques ◽  
Intramolecular Association ◽  
C Nmr

A series of derivatives with various oxygen functionalities in positions 17,22a or 19,20 was prepared from diene I and olefin XVI by addition and oxidation reactions. The structure of the obtained compounds was confirmed by 1H NMR, 13C NMR and IR spectroscopy. The kind of intramolecular association of the 17α-hydroxy group was studied in connection with modification of the side chain and substitution in position 22a. Complete assignment of the hydrogen signals and most of the coupling constants was accomplished using a combination of 1D and 2D NMR techniques. The 1H and 13C NMR spectra are discussed.

Crosslinking Density of Silk Fibroin – Rice Starch Hydrogels Modified with Trisodium Trimetaphosphate

2013 ◽  
Vol 446-447 ◽  
pp. 366-372 ◽  
Author(s):  
Anucha Racksanti ◽  
Sorapong Janhom ◽  
Sittiporn Punyanitya ◽  
Ruangsri Watanesk ◽  
Surasak Watanesk
Keyword(s):  
Silk Fibroin ◽  
Nmr Spectra ◽  
Crosslinking Density ◽  
Proton Nuclear Magnetic Resonance ◽  
Rice Starch ◽  
Infrared Spectrometry ◽  
Solution Casting ◽  
H Nmr ◽  
Nmr Spectrometry ◽  
Mb Adsorption

Silk fibroin (SF) and rice starch (RS) are both biopolymers being non-toxic, biocompatible and biodegradable which can be utilized as hydrogels. The aim of this study was to prepare the SF–RS hydrogels modified with trisodium trimetaphosphate (STMP) and determine its crosslinking density for providing a guideline for preparing better quality absorbable hydrogels. The SF–RS hydrogels modified with various percentages of STMP were prepared by solution casting at pH 12 then neutralized to pH 7. The functional groups and molecular linkages of the hydrogels were investigated by Fourier transform infrared spectrometry (FTIR) and proton nuclear magnetic resonance (1H NMR) spectrometry, respectively. Finally, the crosslinking density of the hydrogels was determined by UV/Vis spectrophotometry via the measurement of the relative amount of methylene blue (RMB) bound to the hydrogels. Results from the FTIR and 1H NMR spectra revealed that linkages within the hydrogels occurred mainly between the O–H groups of RS and the triphosphate groups of STMP. From the MB adsorption study, the crosslinking density of the SF–RS hydrogel with 1.0 %w/w STMP at the 60 min saturation time was approximately 63 %.

scholarly journals Structural requirements for the utilization of ascorbate analogues in the prolyl 4-hydroxylase reaction

1994 ◽  
Vol 300 (1) ◽  
pp. 75-79 ◽  
Author(s):  
G Tschank ◽  
J Sanders ◽  
K H Baringhaus ◽  
F Dallacker ◽  
K I Kivirikko ◽  
...  
Keyword(s):  
Negative Charge ◽  
Substrate Inhibition ◽  
Side Chain ◽  
Structural Requirements ◽  
Response Behaviour ◽  
Structural Analogues ◽  
Microsomal Hydroxylation ◽  
Ring Position ◽  
Charged Group ◽  
Positively Charged

The ability of structural analogues of ascorbate to serve as substitutes for this reducing agent in the prolyl 4-hydroxylase reaction was studied. In experiments using the purified enzyme, variations of the compounds′ side chain were compatible with co-substrate activity. The presence of very large hydrophobic substituents or a positively charged group caused an increase in the observed Km values. A negative charge and smaller modifications did not change the affinity to the enzyme when compared with L-ascorbate. 6-Bromo-6-deoxy-L-ascorbate had a lower Km than the physiological reductant. Substitution at the -OH group in ring position 3 prevented binding to the enzyme. The same pattern of activity was observed when the full and uncoupled prolyl 4-hydroxylase reactions were studied. The Vmax. values with all compounds were similar. The reaction of microsomal prolyl 4-hydroxylase was supported by D-isoascorbate, O6-tosyl-L-ascorbate and 5-deoxy-L-ascorbate, giving the same dose-response behaviour as L-ascorbate itself. Again, 6-bromo-6-deoxy-L-ascorbate gave a lower Km and a similar Vmax. value. L-Ascorbic acid 6-carboxylate produced substrate inhibition at concentrations above 0.3 mM. The Km and Vmax. values calculated from concentrations up to 0.2 mM were similar to those of L-ascorbate. The enzyme activity observed with 6-amino-6-deoxy-L-ascorbate was very low in the microsomal hydroxylation system. The calculated Vmax. value was lower than that of L-ascorbate, suggesting a restriction of the access of this compound to the enzyme.

Tautomerization tendencies of 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, and cyclic β-keto esters of five- and six-membered rings

2001 ◽  
Vol 79 (4) ◽  
pp. 448-454 ◽  
Author(s):  
Antonio Rojas ◽  
Alfonso Perez-Encabo ◽  
Ignacio Herraiz-Sierra ◽  
Carlos A Blanco
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Nmr Spectra ◽  
Tautomeric Equilibrium ◽  
Concentration Effects ◽  
Keto Esters ◽  
H Nmr ◽  
Kinetics Studies ◽  
Dilute Aqueous Solution ◽  
C Nmr

NMR and kinetics studies of the tautomeric equilibrium of 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, and methyl 2-oxocycloalkanecarboxylates of five- and six-membered rings have been carried out. By comparing 1H NMR and 13C NMR spectra recorded in D2O–DOCD3 and CDCl3, with those results derived using a bromination kinetic procedure in dilute aqueous solution, information concerning tautomeric interconversion is provided. Some discussions considering ionisation equilibria and rate constants involved have also been considered. Solvent and concentration effects on keto-enol equilibria have also been discussed.Key words: 2-acetylcycloalkanones, 2-acetyl-1,3-cycloalkanediones, methyl 2-oxocycloalkanecarboxylates, equilibrium, tautomerization, ionization.

Analysis of 1H-NMR spectra of cinnamaldehyde type model substances of lignin

1980 ◽  
Vol 45 (2) ◽  
pp. 330-334 ◽  
Author(s):  
Tibor Liptaj ◽  
Milan Remko ◽  
Ján Polčin
Keyword(s):  
Double Bond ◽  
Nmr Spectra ◽  
Side Chain ◽  
Type Model ◽  
Stable Conformer ◽  
Spectra Analysis ◽  
H Nmr ◽  
Nmr Data ◽  
Lignin Model ◽  
Model Substances

1H-NMR spectra of the following lignin model substances have been analyzed: cinnamaldehyde, 2-methoxycinnamaldehyde, 3-methoxycinnamaldehyde, 4-methoxycinnamaldehyde, 3,4-dimethoxycinnamaldehyde, 3-methoxy-4-hydroxycinnamaldehyde and 3,4,5-trimethoxycinnamaldehyde. From the NMR spectra analysis it follows that the studied compounds exist in solutions as trans isomers. Theoretical (PCILO) calculations in agreement with the NMR data have shown that the more stable conformer has trans orientation of C=O group with respect to the double bond of the conjugated side chain.

Effect of Concentration on the Ionic Interaction between Polystyrene Sulfonate and Cationic Surfactant in Aqueous Solution

2018 ◽  
Vol 916 ◽  
pp. 24-29
Author(s):  
Agus Haryono ◽  
Muhammad Ghozali ◽  
Sri Budi Harmami ◽  
Yenny Meliana
Keyword(s):  
Aqueous Solution ◽  
Nmr Spectra ◽  
Polymer Concentration ◽  
Polystyrene Sulfonate ◽  
Ionic Interaction ◽  
Anionic Polymer ◽  
H Nmr ◽  
Sulfonation Degree ◽  
Polystyrene Waste

Polystyrene sulfonate (PSS) were prepared by sulfonation method of polystyrene using sulfuric acid. Abundant amount of polystyrene waste can be reused as a coagulant, membrane for polymer fuel cell and anionic-cationic polymer interactions. The characterization of PSS was carried out by using UV-Vis, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectra, molecular weight and analysis of sulfonation degree. The degree of sulfonation was obtained at 94,18%. Ionic interaction between anionic polymer PSS and cetyltrimethylammonium bromide (CTAB) as cationic compound in aqueous solution were analyzed by using dynamic light scattering (DLS), conductometry and fluorimetry. Behavior of conductivity have been calculated the critical micelle concentration (cmc). The FTIR and 1H-NMR spectra showed the ionic interaction between PSS and CTAB. This ionic interaction can be controlled by changing the polymer concentration.

Derivatives of 5α-androstan-3α- and 3β-ol with acrylonitrile side chain

1991 ◽  
Vol 56 (12) ◽  
pp. 2906-2916 ◽  
Author(s):  
Vladimír Pouzar ◽  
Hana Chodounská ◽  
Ivan Černý ◽  
Pavel Drašar
Keyword(s):  
Double Bond ◽  
Nmr Spectra ◽  
Sodium Hydride ◽  
Coupling Constants ◽  
Side Chain ◽  
H Nmr ◽  
Derivatives Of

Aldehydes II - III were reacted with diethyl cyanomethylphosphonate and sodium hydride in 1,2-dimethoxyethane to give the respective pairs of unsaturated nitriles IVa and Va, VIa and VIIa, and VIIIa and IXa differing in configuration at the 20(21)-double bond. The pure isomers were obtained by chromatography on alumina, and the configuration at the double bond in them has been established on the basis of the coupling constants J(20, 21) in their 1H NMR spectra. Nitriles IVa - VIIa and IXa were converted via the corresponding hydroxy derivatives into hemisuccinates IVd - VIId and IXd, and into β-D-glucosides IVe - VIIe and IXe.

Complete assignment of the 1H and 13C NMR spectra and conformational analysis of bonellin dimethyl ester

2004 ◽  
Vol 08 (12) ◽  
pp. 1376-1382 ◽  
Author(s):  
Paavo H. Hynninen ◽  
Juho Helaja ◽  
Franz-Peter Montforts ◽  
Claudia M. Müller
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Dimethyl Ester ◽  
Coupling Constants ◽  
Side Chain ◽  
Clear Correlation ◽  
High Tendency ◽  
H Nmr ◽  
Broad Signal ◽  
Previous Assignment

The use of a high-field NMR instrument (ν(1 H ) = 500 MHz ) and 2-dimensional NMR techniques (HMQC, HMBC, ROESY) enabled us to fully assign the 1 H and 13 C chemical shifts of bonellin dimethyl ester. The β-pyrrolic proton of C -3 appeared as a broad singlet at δ = 8.93, whereas that of C -8 gave a quartet with δ = 8.69 and 4J H - H = |1.28| Hz . The C -21 methyl protons appeared as a doublet with δ = 3.55 and 4J H - H = |1.07| Hz , while the C -71 methyl protons afforded a doublet with δ = 3.51 and 4J H - H = |1.28| Hz . These results suggest that the β-pyrrolic carbons of ring A belong to the aromatic 18 π-electron [18]diazaannulene delocalization pathway, whereas those of ring B remain outside the aromatic pathway. The broadening of the C -3 β-pyrrolic proton signal can be attributed to the allylic 3- CH - 21- CH 3 coupling and the 3- CH - 21- NH coupling. At 330 K, the tautomeric exchange 21- NH a ⇌ 23- NH b is fast and only one broad signal at δ = -2.49 is seen for these protons. The ROESY spectrum showed clear correlation signals between the 182- CH 3 and 171- CH 2 protons, the 182- CH 3 and 174- CH 3 protons, as well as between the 181- CH 3 and 17- CH protons. These results are compatible with the previous assignment that the absolute configuration at C-17 is S. Application of spin simulation enabled us to determine the chemical shifts and the 3J H - H coupling constants of the 17-propionate side-chain. The 3J H - H -values were used to calculate the populations for the 171-17 and 172-171 rotamers. A relatively high population value of 0.41 was found for the 171-17 g--rotamer, whose methoxycarbonylmethyl group points to the C -15 methine-bridge. This was interpreted as explaining the high tendency of bonellin to form anhydrobonellin. The rotational freedoms in the 13-propionate side-chain were studied by measuring the 1 H NMR spectra of the side-chain at temperatures between 300 and 195 K. At 300 K, the 131- and 132- CH 2 proton signals appeared as deceptively simple triplets, which at 195 K were split into complex multiplets. At 195 K, the signal arising from the 131- CH 2 protons exhibited more splitting, which indicates that these protons have less rotational freedom than the 132- CH 2 protons.

Crystal structure of methyl,2-mercaptopyrimidinatomercury(II)

1978 ◽  
Vol 56 (4) ◽  
pp. 560-563 ◽  
Author(s):  
Chung Chieh
Keyword(s):  
Crystal Structure ◽  
Aqueous Solution ◽  
Nmr Spectra ◽  
Heavy Atom ◽  
Pyrimidine Ring ◽  
Optically Active ◽  
Hydrogen Atoms ◽  
H Nmr ◽  
R Factor ◽  
Heavy Atom Method

Methyl,2-mercaptopyrimidinatomercury(II) was synthesized from methylmercuric hydroxide and 2-mercaptopyrimidine in aqueous solution. The crystal is orthorhombic with a = 4.063(2), b = 9.901(4), c = 18.808(15) Å, Dm = 2.88(1), Z = 4, Dc = 2.867 g cm−3, space group P212121. The structure was solved by the heavy atom method using 605 diffractometer measured reflections. The final R factor was 0.069. The key bond lengths and angles are: Hg—S, 2.39(2) Å, Hg—CH3, 2.13(6) Å, [Formula: see text] 174°. The CH3HgS— group bends out of the plane of the pyrimidine ring and the Hg atom interacts rather strongly with one of the ring nitrogens with an Hg—N distance of 2.83 Å. However, the Hg … N interaction is very labile in solution, since the two hydrogen atoms in the meta positions are equivalent from the 1H nmr spectra in both CDCl3 and DMSO solutions. The solution of the compound is not optically active.

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