Binding of magnesium and lanthanum ions to heparin in the presence of sodium ions. A relationship between 13C chemical shift displacements and counterion condensation theory

1987 ◽  
Vol 65 (8) ◽  
pp. 1739-1745 ◽  
Author(s):  
Photis Dais ◽  
Qin-Ji Peng ◽  
Arthur S. Perlin
Keyword(s):  
Chemical Shift ◽  
Sodium Ions ◽  
Univalent Cations ◽  
Counterion Condensation ◽  
Ionic Radii ◽  
Counterion Binding ◽  
Binding Preference ◽  
13C Chemical Shift ◽  
Site Binding ◽  
C Nmr

Interactions between beef lung heparin and Mg2+ and La3+ counterions, in the presence of sodium ions, have been investigated by 13C-nmr spectroscopy. The chemical shift displacements observed for the carbons of the main disaccharide unit of heparin, when analysed on the basis of counterion condensation theory, indicate that the association between the heparin polyanion and Mg2+ is a delocalized process. This is analogous to the Ca2+/Na+/heparin system, despite the fact that the binding affinity of heparin for Ca2+ is stronger than that for Mg2+. By contrast, the interaction with La3+ is in excess of the theoretical predicted, which suggests that there is at least a partial site-binding of this counterion. In Ca2+/M+/heparin systems in which M+ = Na+ or K+, the selective binding preference of heparin for the univalent cations may be related to the order of their crystallographic ionic radii. A critical assessment is offered of the validity of this nmr spectroscopic approach to the study of counterion binding to heparin.

Electric condensation of divalent counterions by humic acid nanoparticles

2016 ◽  
Vol 13 (1) ◽  
pp. 76 ◽  
Author(s):  
Herman P. van Leeuwen ◽  
Raewyn M. Town
Keyword(s):  
Humic Acid ◽  
Charge Density ◽  
Double Layer ◽  
Ion Pairs ◽  
Ion Pairing ◽  
Counterion Condensation ◽  
Counterion Binding ◽  
Satisfactory Description ◽  
Poisson Boltzmann ◽  
Very High

Environmental context Humic acids are negatively charged soft nanoparticles that play a governing role in the speciation of many ionic and molecular compounds in the environment. The charge density in the humic acid nanoparticle can be very high and the binding of divalent cations such as Ca2+ appears to go far beyond traditional ion pairing or Poisson–Boltzmann electrostatics. A two-state approach, combining counterion condensation in the intraparticulate double layer and classical Donnan partitioning in the bulk of the particle, provides a satisfactory description of the physicochemical speciation. Abstract Experimental data for divalent counterion binding by soil humic acid nanoparticles are set against ion distributions as ensuing from continuous Poisson–Boltzmann electrostatics and a two-state condensation approach. The results demonstrate that Poisson–Boltzmann massively underestimates the extent of binding of Ca2+ by humic acid, and that electric condensation of these counterions within the soft nanoparticulate body must be involved. The measured stability of the Ca2+–humic acid associate is also much greater than that predicted for ion pairing between single Ca2+ ions and monovalent negative humic acid sites, which also points to extensive electrostatic cooperativity within the humic acid particle. At sufficiently high pH, the charge density inside the humic acid entity may indeed become so high that the bulk particle attains a very high and practically flat potential profile throughout. At this limit, all the intraparticulate Ca2+ is at approximately the same electrostatic potential and the status of individual ion pairs has become immaterial. A two-state model, combining counterion condensation in the charged intraparticulate part of the double layer at the particle–medium interface and Donnan partitioning in the uncharged bulk of the humic acid particle, seems to lead the way to adequate modelling of the divalent counterion binding for various particle sizes and different ionic strengths.

Determination of chemical shifts in 6-condensed syringylic lignin model compounds

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lucas Lagerquist ◽  
Jani Rahkila ◽  
Patrik Eklund
Keyword(s):  
Chemical Shift ◽  
Methoxy Group ◽  
Chemical Shifts ◽  
Model Compounds ◽  
Correlation Peak ◽  
Lignin Model Compounds ◽  
Benzylic Alcohols ◽  
Lignin Model ◽  
C Nmr

Abstract A small library of 6-substituted syringyl model compounds with aliphatic, carboxylic, phenylic, benzylic alcohols and brominated substituents were prepared. The influence of the substituents on the chemical shifts of the compounds was analyzed. All of model compounds showed a characteristic increase in the 13C NMR chemical shift of the methoxy group vicinal to the substitution. This 13C NMR peak and its corresponding correlation peak in HSQC could potentially be used to identify 6-condensation in syringylic lignin samples.

scholarly journals 1H, 15N and 13C chemical shift assignments of the La motif and RRM1 from human LARP6

2015 ◽  
Vol 9 (2) ◽  
pp. 337-340 ◽  
Author(s):  
Luigi Martino ◽  
Nicholas J. H. Salisbury ◽  
Paul Brown ◽  
Geoff Kelly ◽  
R. Andrew Atkinson ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Chemical Shift Assignments ◽  
13C Chemical Shift

scholarly journals 13Check_RNA: a tool to evaluate 13C chemical shift assignments of RNA

2018 ◽  
Vol 34 (23) ◽  
pp. 4124-4126 ◽  
Author(s):  
A A Icazatti ◽  
O A Martin ◽  
M Villegas ◽  
I Szleifer ◽  
J A Vila
Keyword(s):  
Chemical Shift ◽  
Chemical Shift Assignments ◽  
13C Chemical Shift

13C NMR CHEMICAL SHIFT CALCULATION FOR THE 1, 1'-DISUBSTITUTED FERROCENE COMPOUNDS

1986 ◽  
Vol 2 (01) ◽  
pp. 73-76
Author(s):  
Li Cun ◽  
◽  
Wu Weixiong ◽  
Pen Xin ◽  
Chao Qirong ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Nmr Chemical Shift ◽  
Ferrocene Compounds ◽  
Shift Calculation ◽  
C Nmr

Carbon magnetic resonance studies of some phenyl, furyl and thienyl organometallics. Some comments on carbon-metal scalar coupling

1974 ◽  
Vol 27 (2) ◽  
pp. 417 ◽  
Author(s):  
D Doddrell ◽  
KG Lewis ◽  
CE Mulquiney ◽  
W Adcock ◽  
W Kitching ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Scalar Coupling ◽  
Coupling Constant ◽  
Aryl Substituent ◽  
Magnetic Resonance Studies ◽  
Thienyl Group ◽  
13C Chemical Shift

13C chemical shift variations within a series of phenyl, furyl and thienyl Group IVB organometallics appear to be best understood in terms of the usual alkyl and aryl substituent effects on 13C chemical shifts and not variations in dπ ?pπ metal-aryl interactions. Large changes in 13C-metal scalar coupling constants have been observed suggesting that other factors besides the s-character of the carbon-metal bond is responsible in determining the coupling constant.

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