scholarly journals Potentially Mistaking Enantiomers for Different Compounds Due to the Self-Induced Diastereomeric Anisochronism (SIDA) Phenomenon

Symmetry ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1106
Author(s):  
Andreas Baumann ◽  
Alicja Wzorek ◽  
Vadim A. Soloshonok ◽  
Karel D. Klika ◽  
Aubry K. Miller
Keyword(s):  
Solid State ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
The Self ◽  
Equal Concentration ◽  
Chiral Compounds ◽  
Intermolecular Noe ◽  
Association Preference ◽  
Nuclear Overhauser ◽  
And Diffusion

The NMR phenomenon of self-induced diastereomeric anisochronism (SIDA) was observed with an alcohol and an ester. The alcohol exhibited large concentration-dependent chemical shifts (δ’s), which initially led us to erroneously consider whether two enantiomers were in fact atropisomers. This highlights a potential complication for the analysis of chiral compounds due to SIDA, namely the misidentification of enantiomers. A heterochiral association preference for the alcohol in CDCl3 was determined by the intermolecular nuclear Overhauser effect (NOE) and diffusion measurements, the same preference as found in the solid state. The ester revealed more subtle effects, but concentration-dependent δ’s, observation of intermolecular NOE’s, as well as distinct signals for the two enantiomers in a scalemic sample all indicated the formation of associates. Intermolecular NOE and diffusion measurements indicated that homochiral association is slightly preferred over heterochiral association in CDCl3, thus masking association for enantiopure and racemic samples of equal concentration. As observed with the alcohol, heterochiral association was preferred for the ester in the solid state. The potential problems that SIDA can cause are highlighted and constitute a warning: Due care should be taken with respect to conditions, particularly the concentration, when measuring NMR spectra of chiral compounds. Scalemic samples of both the alcohol and the ester were found to exhibit the self-disproportionation of enantiomers (SDE) phenomenon by preparative TLC, the first report of SDE by preparative TLC.

scholarly journals Characterization of Halogen Bonded Adducts in Solution by Advanced NMR Techniques

2017 ◽  
Author(s):  
Gianluca Ciancaleoni
Keyword(s):  
Nuclear Overhauser Effect ◽  
Halogen Bonding ◽  
X Ray Crystallography ◽  
Diffusion Nmr ◽  
Overhauser Effect ◽  
Crucial Information ◽  
Nmr Techniques ◽  
Nuclear Overhauser ◽  
And Diffusion

In the last 20 years, a huge amount of experimental results about halogen bonding (XB) has been produced. Most of the systems have been characterized by solid state X-ray crystallography, whereas in solution the only routine technique is the titration (by using 1H and 19F NMR, IR, UV-Vis or Raman spectroscopies, depending on the nature of the system), with the aim of characterizing the strength of the XB interaction. Unfortunately, the titration techniques have many intrinsic limitations and they should be coupled with other, more sophisticated techniques to have an accurate and detailed description of the geometry and stoichiometry of the XB adduct in solution. In this review, it will be shown how crucial information about XB adducts can be obtained by advanced NMR techniques, as Nuclear Overhauser Effect-based Spectroscopies (NOESY, ROESY, HOESY…) and diffusion NMR techniques (PGSE or DOSY).

scholarly journals Changes in protein hydration dynamics by encapsulation or crowding of ubiquitin: strong correlation between time-dependent Stokes shift and intermolecular nuclear Overhauser effect

RSC Advances ◽  
2019 ◽  
Vol 9 (63) ◽  
pp. 36982-36993 ◽  
Author(s):  
Philipp Honegger ◽  
Esther Heid ◽  
Stella Schmode ◽  
Christian Schröder ◽  
Othmar Steinhauser
Keyword(s):  
Strong Correlation ◽  
Nuclear Overhauser Effect ◽  
Stokes Shift ◽  
Time Dependent ◽  
Protein Hydration ◽  
Overhauser Effect ◽  
Intermolecular Noe ◽  
Nuclear Overhauser ◽  
Local Protein ◽  
Hydration Dynamics

Changes in local protein hydration dynamics caused by encapsulation or crowding are reflected in the TDSS and the intermolecular NOE alike.

Nuclear Overhauser Effect (NOE) Enhancement of11B NMR Spectra of Borane Adducts in the Solid State

2006 ◽  
Vol 128 (21) ◽  
pp. 6782-6783 ◽  
Author(s):  
Sharon E. Ashbrook ◽  
Nicholas G. Dowell ◽  
Ivan Prokes ◽  
Stephen Wimperis
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Nuclear Overhauser Effect ◽  
Overhauser Effect ◽  
Nuclear Overhauser

A nuclear Overhauser effect difference study of the solution conformation of (6R)-prostaglandin I1

1980 ◽  
Vol 58 (23) ◽  
pp. 2649-2659 ◽  
Author(s):  
George Kotovych ◽  
Gerdy H. M. Aarts
Keyword(s):  
Proton Magnetic Resonance ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Solution Conformation ◽  
Magnetic Resonance Studies ◽  
Overhauser Effect ◽  
Complete Assignment ◽  
Effect Difference ◽  
Nuclear Overhauser

Proton magnetic resonance studies at 400 MHz allowed the complete assignment of the spectra for (6R)-prostaglandin I1 in phosphate buffer and in CDCl3 solutions. The spectral analysis was based on the nuclear Overhauser effect difference measurements, which also provide accurate chemical shifts and coupling constants. Conformational differences in the two solvents for the ring portion of the molecule are indicated.

Cation-dependent structural features of β-casein-(1–25)

2001 ◽  
Vol 356 (1) ◽  
pp. 277-286 ◽  
Author(s):  
Keith J. CROSS ◽  
N. Laila HUQ ◽  
Wendy BICKNELL ◽  
Eric C. REYNOLDS
Keyword(s):  
Calcium Ions ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
Resonance Assignments ◽  
Structural Features ◽  
Complete Sequence ◽  
Sequence Motif ◽  
Sodium Ions ◽  
Medium Range ◽  
Nuclear Overhauser

Complete sequence-specific, proton-resonance assignments have been determined for the calcium phosphate-stabilizing tryptic peptide β-casein-(1–25) containing the phosphorylated sequence motif Ser(P)17-Ser(P)-Ser(P)-Glu-Glu21. Spectra of the peptide have been recorded, in separate experiments, in the presence of excess ammonium ions, sodium ions and calcium ions, and of the dephosphorylated peptide in the presence of excess sodium ions. We observed significant changes to chemical shifts for backbone and side-chain resonances that were dependent upon the nature of the cation present. Medium-range nuclear Overhauser effect (nOe) enhancements, characteristic of small structured regions in the peptide, were observed and also found to be cation dependent. The secondary structure of the peptide was characterized by sequential and medium-range (i, i+2/3/4, which denotes an interaction between residue i and residue i+2, i+3 or i+4 in the peptide) nOe connectivities, and Hα chemical shifts. Four structured regions were identified in the calcium-bound peptide: residues Arg1 to Glu4 were involved in a loop-type structure, and residues Val8 to Glu11, Ser(P)17 to Glu20 and Glu21 to Thr24 were implicated in β-turn conformations. Comparison of the patterns of medium-range nOe connectivities in β-casein-(1–25) with those in αS1-casein-(59–79) suggest that the two peptides have distinctly different conformations in the presence of calcium ions, despite having a high degree of sequential and functional similarity.

scholarly journals Integrative protein modeling in RosettaNMR from sparse paramagnetic restraints

2019 ◽  
Author(s):  
Georg Kuenze ◽  
Richard Bonneau ◽  
Julia Koehler Leman ◽  
Jens Meiler
Keyword(s):  
Protein Structure ◽  
Computational Methods ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
High Accuracy ◽  
Ligand Docking ◽  
Nmr Structure Determination ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
Nmr Restraints

AbstractComputational methods to predict protein structure from nuclear magnetic resonance (NMR) restraints that only require assignment of backbone signals hold great potential to study larger proteins and complexes. Additionally, computational methods designed to work with sparse data add atomic detail that is missing in the experimental restraints, allowing application to systems that are difficult to investigate. While specific frameworks in the Rosetta macromolecular modeling suite support the use of certain NMR restraint types, use of all commonly measured restraint types together is precluded. Here, we introduce a comprehensive framework into Rosetta that reconciles CS-Rosetta, PCS-Rosetta and RosettaNMR into a single framework, that, in addition to backbone chemical shifts and nuclear Overhauser effect distance restraints, leverages NMR restraints derived from paramagnetic labeling. Specifically, RosettaNMR incorporates pseudocontact shifts, residual dipolar couplings, and paramagnetic relaxation enhancements, measured at multiple tagging sites. We further showcase the generality of RosettaNMR for various modeling challenges and benchmark it on 28 structure prediction cases, eight symmetric assemblies, two protein-protein and three protein-ligand docking examples. Paramagnetic restraints generated more accurate models for 85% of the benchmark proteins and, when combined with chemical shifts, sampled high-accuracy models (≤ 2Å) in 50% of the cases.Significance StatementComputational methods such as Rosetta can assist NMR structure determination by employing efficient conformational search algorithms alongside physically realistic energy functions to model protein structure from sparse experimental data. We have developed a framework in Rosetta that leverages paramagnetic NMR data in addition to chemical shift and nuclear Overhauser effect restraints and extends RosettaNMR calculations to the prediction of symmetric assemblies, protein-protein and protein-ligand complexes. RosettaNMR generated high-accuracy models (≤ 2Å) in 50% of cases for a benchmark set of 28 monomeric and eight symmetric proteins and predicted protein-protein and protein-ligand interfaces with up to 1Å accuracy. The method expands Rosetta’s rich toolbox for integrative data-driven modeling and promises to be broadly useful in structural biology.

scholarly journals Recognition Selectivities of Lasso-Type Pseudo[1]rotaxane Based on a Mono-Ester-Functionalized Pillar[5]arene

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2693
Author(s):  
Wen-Xue Zhang ◽  
Lu-Zhi Liu ◽  
Wen-Gui Duan ◽  
Qing-Qing Zhou ◽  
Cui-Guang Ma ◽  
...  
Keyword(s):  
Self Assembly ◽  
Nuclear Overhauser Effect ◽  
Great Influence ◽  
Ester Group ◽  
The Self ◽  
Side Chain ◽  
Overhauser Effect ◽  
Methoxy Groups ◽  
Complex Models ◽  
Nuclear Overhauser

Two types of mono-ester-functionalized pillar[5]arenes, P1 and P2, bearing different side-chain groups, were synthesized. Their host–guest complexation and self-inclusion properties were studied by 1H NMR and 2D nuclear overhauser effect spectroscopy (NOESY) NMR measurements. The results showed that the substituents on their phenolic units have a great influence on the self-assembly of both pillar[5]arenes, although they both could form stable pseudo[1]rotaxanes at room temperature. When eight bulky 4-brombutyloxy groups were capped on the cavity, instead of methoxy groups, pseudo[1]rotaxane P1 became less stable and its locked ester group in the inner space of cavity was not as deep as P2, leading to distinctly different host–guest properties between P1 and P2 with 1,6-dibromohexane. Moreover, pillar[5]arene P1 displayed effective molecular recognition toward 1,6-dichlorohexane and 1,2-bromoethane among the guest dihalides. In addition, the self-complex models and stabilities between P1 and P2 were also studied by computational modeling and experimental calculations.

Proton magnetic resonance spectra of catechin and bromocatechin derivatives: C6- vs. C8-substitution

1986 ◽  
Vol 64 (10) ◽  
pp. 1998-2005 ◽  
Author(s):  
E. Kiehlmann ◽  
A. S. Tracey
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
Overhauser Effect ◽  
Resonance Frequencies ◽  
The Difference ◽  
Nuclear Overhauser ◽  
Unambiguous Assignment ◽  
Magnetic Resonance Spectra

The 1Hmr spectra of 20 catechin derivatives substituted at C-6/C-8 by bromine and/or hydrogen and at oxygen by methyl, acetyl, and/or hydrogen have been analyzed in deuterated acetone, acetonitrile, and chloroform. Because of its dependence on the nature of the solvent and of the oxygen substituent, the difference between H-6 and H-8 chemical shifts has been found to be an unreliable criterion for the distinction between 8-bromo and 6-bromo isomers. In methylated catechins, double irradiation of H-8 and H-6 enhances one (MeO-7) and two (MeO-5 and MeO-7) methoxy signals, respectively, via the nuclear Overhauser effect. This permits unambiguous assignment of chemical shifts to all ring A protons. The H-6 and H-8 resonance frequencies of catechin have been determined by decoupling of the OH-5 and OH-7 protons.

A nuclear Overhauser effect difference study and a two-dimensional J proton magnetic resonance study of (6S)-prostaglandin I1

1981 ◽  
Vol 59 (10) ◽  
pp. 1449-1454 ◽  
Author(s):  
George Kotovych ◽  
Gerdy H. M. Aarts ◽  
Tom T. Nakashima
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Two Dimensional ◽  
Overhauser Effect ◽  
Effect Difference ◽  
Proton Resonances ◽  
Nuclear Overhauser

High-field nuclear Overhauser effect difference measurements allowed the assignment of the proton resonances for (6S)-prostaglandin I1 in phosphate buffer solutions. The two-dimensional J proton magnetic resonance experiments complemented these studies, as they also allowed the structure of several multiplets to be obtained when these multiplets are hidden by nearby resonances in a normal spectrum. The chemical shifts and coupling constants are compared with the data obtained previously for (6R)-prostaglandin I1.

123Te and 125Te Fourier Transform NMR Investigations

1977 ◽  
Vol 32 (11) ◽  
pp. 1263-1265 ◽  
Author(s):  
K. U. Buckler ◽  
J. Kronenbitter ◽  
. Lutz ◽  
A. Nollle
Keyword(s):  
Fourier Transform ◽  
Nuclear Overhauser Effect ◽  
Chemical Shifts ◽  
Magnetic Moments ◽  
Relaxation Times ◽  
Dipole Interaction ◽  
High Accuracy ◽  
Overhauser Effect ◽  
Nuclear Overhauser ◽  
Nmr Signals

Abstract The NMR signals of 123Te and 125Te have been observed in solutions of K2TeO3 and Na2TeO3 in D2O. In these solutions the ratios of Larmor frequencies ν(125Te)/ν(123Te), ν(125Te)/v(2H) and ν(125Te)/ν(23Na) have been determined with high accuracy. With the measured chemical shifts of 2H, 23Na, 125Te relative to infinitely diluted solutions the ratios of the Larmor frequencies are extrapolated and values of the magnetic moments are given. The relaxation times T1 and T2 are very different for 125Te in TeO32-: a ratio T1/T2 of 8.2 ± 0.4 has been found. No nuclear Overhauser effect due to dipole-dipole interaction of 125Te with the water protons has been detected.

Sign in / Sign up

Export Citation Format

Share Document