Hadamard magnetization transfers achieve dramatic sensitivity enhancements in homonuclear multidimensional NMR correlations of labile sites in proteins, polysaccharides and nucleic acids

EXSY, TOCSY and NOESY lie at the foundation of homonuclear NMR experiments in organic and pharmaceutical chemistry, as well as in structural biology. Limited magnetization transfer efficiency is an intrinsic downside of these methods, particularly when targeting rapidly exchanging species such as labile protons ubiquitous in polysaccharides, sidechains and backbones of proteins, and in bases and sugars of nucleic acids: the fast decoherence imparted on these protons through solvent exchanges, greatly reduces their involvement in homonuclear correlation experiments. We have recently discussed how these decoherences can be visualized as an Anti-Zeno Effect, that can be harnessed to enhance the efficiency of homonuclear transfers within Looped PROjected SpectroscopY (L-PROSY) leading to 200-300% enhancements in NOESY and TOCSY cross-peaks for amide groups in biomolecules. This study demonstrates that even larger sensitivity gains per unit time, equivalent to reductions by several hundred-folds in the duration of experiments, can be achieved by looping inversion or using saturation procedures. In the ensuing experiments a priori selected frequencies are encoded according to Hadamard recipes, and subsequently resolved along the indirect dimension via linear combinations. Magnetization-transfer (MT) processes reminiscent of those occurring in CEST provide significant enhancements in the resulting cross-peaks, in only a fraction of acquisition time of a normal 2D experiment. The effectiveness of the ensuing three-way polarization transfer interplay between water, labile and non-labile protons was corroborated experimentally for proteins, homo-oligosaccharides and nucleic acids. In all cases, cross-peaks barely detectable in conventional 2D NMR counterparts, were measured ca. 10-fold faster and with 200-600% signal enhancements by the Hadamard MT counterparts

Implicit Regularization and Renormalization of QCD

We apply the Implicit Regularization Technique (IR) in a non-abelian gauge theory. We show that IR preserves gauge symmetry as encoded in relations between the renormalizations constants required by the Slavnov-Taylor identities at the one loop level of QCD. Moreover, we show that the technique handles divergencies in massive and massless QFT on equal footing.Comment: (11 pages, 2 figures

On the equivalence between Implicit Regularization and Constrained Differential Renormalization

Constrained Differential Renormalization (CDR) and the constrained version of Implicit Regularization (IR) are two regularization independent techniques that do not rely on dimensional continuation of the space-time. These two methods which have rather distinct basis have been successfully applied to several calculations which show that they can be trusted as practical, symmetry invariant frameworks (gauge and supersymmetry included) in perturbative computations even beyond one-loop order. In this paper, we show the equivalence between these two methods at one-loop order. We show that the configuration space rules of CDR can be mapped into the momentum space procedures of Implicit Regularization, the major principle behind this equivalence being the extension of the properties of regular distributions to the regularized ones.Comment: 16 page

Regularization Independent Analysis of the Origin of Two Loop Contributions to N=1 Super Yang-Mills Beta Function

We present a both ultraviolet and infrared regularization independent analysis in a symmetry preserving framework for the N=1 Super Yang-Mills beta function to two loop order. We show explicitly that off-shell infrared divergences as well as the overall two loop ultraviolet divergence cancel out whilst the beta function receives contributions of infrared modes.Comment: 7 pages, 2 figures, typos correcte

Direct Evidence for Hydrogen Bonding in Glycans : A Combined NMR and Molecular Dynamics Study

We introduce the abundant hydroxyl groups of glycans as NMR handle's and structural probes to expand the repertoire of tools for structure function studies on glycans in solution. To this end, we present the facile detection and assignment of hydroxyl groups in a Wide range of sample concentrations (0.5-1700 mM) and temperatures, ranging from -5 to 25 degrees C.,We then exploit this information to directly detect hydrogen bonds, well-known for their importance in molecular structural determination through NMR. Via HSQC-TOCSY, we were able to determine the directionality; of these hydrogen bonds in sucrose Furthermore, by means Of molecular dynamics simulations in conjunction with NMR, we establish that one Out of the three detected hydrogen bonds arises from intermolecular interactions. This finding may shed light on glycan glycan interactions and glycan recognition by proteins.AuthorCount:4;</p

Glycan OH Exchange Rate Determination in Aqueous Solution: Seeking Evidence for Transient Hydrogen Bonds

Hydrogen bonds (Hbonds) are important stabilizing forces in biomolecules. However, for glycans in aqueous solution, direct NMR detection of Hbonds is elusive because of their transient nature. Here, we present Isotope-based Natural-abundance TOtal correlation eXchange SpectroscopY (INTOXSY), a new ¹H–¹³C heteronuclear single quantum coherence–total correlation spectroscopy based method, to extract OH groups’ exchange rate constants (<i>k</i>_ex) for molecules in natural ¹³C abundance and show that OH Hbonds can be inferred from “slower” H/D <i>k</i>_ex. We evaluate <i>k</i>_ex measured with INTOXSY in light of those extracted with line-shape analysis. Subsequently, we use a set of common glycans to establish a <i>k</i>_ex reference basis set and to infer the existence of transient Hbonds involving OH donor groups. Then, we report <i>k</i>_ex values for a series of mono- and disaccharides, as well as for oligosaccharides sialyl Lewis X and β-cyclodextrin, and compare the results with those from the reference set to extract Hbond information. Finally, we utilize NMR experimental data in conjunction with molecular dynamics simulations to establish donor and acceptor Hbond pairs. Our exchange rate measurements indicate that OH/OD exchange rates, <i>k</i>_HD, values <10 s^–1 are consistent with transient Hbond OH groups and potential acceptor groups can be uncovered through MD simulations

Direct Evidence for Hydrogen Bonding in Glycans: A Combined NMR and Molecular Dynamics Study

We introduce the abundant hydroxyl groups of glycans as NMR handles and structural probes to expand the repertoire of tools for structure–function studies on glycans in solution. To this end, we present the facile detection and assignment of hydroxyl groups in a wide range of sample concentrations (0.5–1700 mM) and temperatures, ranging from −5 to 25 °C. We then exploit this information to directly detect hydrogen bonds, well-known for their importance in molecular structural determination through NMR. Via HSQC-TOCSY, we were able to determine the directionality of these hydrogen bonds in sucrose. Furthermore, by means of molecular dynamics simulations in conjunction with NMR, we establish that one out of the three detected hydrogen bonds arises from intermolecular interactions. This finding may shed light on glycan–glycan interactions and glycan recognition by proteins