Micelles for delivery of nitric oxide.

We designed block copolymer pro-amphiphiles and amphiphiles for providing very long-term release of nitric oxide (NO). A block copolymer of N-acryloylmorpholine (AM, as a hydrophile) and N-acryloyl-2,5-dimethylpiperazine (AZd, as a hydrophilic precursor) was synthesized. The poly(N-acryloyl-2,5-dimethylpiperazine) (PAZd) is water-soluble, but chemical reaction of the secondary amines with NO to form a N-diazeniumdiolate (NONOate) converts the hydrophilic PAZd into a hydrophobic poly(sodium-1-(N-acryloyl-2,5-dimethylpiperazin-1-yl)diazen-1-ium-1,2-diolate) (PAZd.

High-resolution 14N-edited 1H-13C correlation NMR experiment to study biological solids.

It was recently shown that nuclear magnetic resonance (NMR) spectra of nitrogen-14 (spin I=1) can be obtained by indirect detection via spin S=1/2 nuclei in powders spinning at the magic angle. An increased number of solid-state NMR methods are now available to tailor sequences for specific purposes, e.g.

Probing amide bond nitrogens in solids using 14N NMR spectroscopy.

A novel two-dimensional nuclear magnetic resonance (NMR) experiment is proposed for indirect observation of 14N nuclei in various types of nitrogen-containing solids. In a method somewhat similar to the heteronuclear single-quantum correlation (HSQC) experiment widely used for protein structure determination in solutions, this technique correlates spin S=1/2 nuclei, e.g.

Dynamics and counterion-dependence of the structures of weakly bound Ag+-P4S3 complexes.

In an earlier publication (J. Am. Chem.

Indirect detection of nitrogen-14 in solid-state NMR spectroscopy.

NMR spectra of (14)N (spin I=1) are obtained by indirect detection in powders spinning at the magic angle. The method relies on the transfer of coherence from a neighboring "spy" nucleus with S=1/2, such as (13)C or (1)H, to single- or double-quantum transitions of (14)N nuclei. The transfer of coherence can occur through a combination of scalar and residual dipolar splittings (RDS); the latter are also known as second-order quadrupole-dipole cross terms.

Study of water dynamics and distances in paramagnetic solids by variable-temperature two-dimensional 2H NMR spectroscopy.

A recently proposed two-dimensional (2)H NMR experiment is used to measure the (2)H (spin I=1) quadrupolar and paramagnetic shift anisotropy interactions in powdered CuCl(2).2D(2)O as a function of temperature. The principal components of the quadrupolar and paramagnetic shift anisotropy tensors and the Euler angles describing the orientations of the tensors in the molecular frame are determined at each temperature.

Experimental observations of water-framework interactions in a hydrated microporous aluminum phosphate.

Differential scanning calorimetry of the hydrated, microporous aluminum phosphate AlPO-14 shows two distinct water losses between room temperature and 120 degrees C, indicating the presence of two types of water in the solid. Multiple-quantum magic angle spinning (MQMAS) (27)Al NMR shows that, while in dehydrated AlPO-14 all aluminum is found in tetrahedral sites, on hydration a significant proportion of the aluminum increases its coordination number to 6. This accounts for the presence of tightly bound water.

Indirect detection of nitrogen-14 in solids via protons by nuclear magnetic resonance spectroscopy.

This Communication describes the indirect detection of 14N nuclei (spin I=1) in solids by nuclear magnetic resonance (NMR) spectroscopy. The two-dimensional correlation method used here is closely related to the heteronuclear multiple quantum correlation (HMQC) experiment introduced in 1979 to study molecules in liquids, which has recently been used to study solids spinning at the magic angle. The difference is that the coherence transfer from neighboring 1H nuclei to 14N is achieved via a combination of J couplings and residual dipolar splittings (RDS).

Dynamics on the microsecond timescale in microporous aluminophosphate AlPO-14 as evidenced by 27Al MQMAS and STMAS NMR spectroscopy.

Multiple-quantum magic angle spinning (MQMAS) and satellite-transition magic angle spinning (STMAS) are two well-known techniques for obtaining high-resolution, or "isotropic", NMR spectra of quadrupolar nuclei. It has recently been shown that dynamics-driven modulation of the quadrupolar interaction on the microsecond timescale results in linewidths in isotropic STMAS spectra that are strongly broadened, while, in contrast, the isotropic MQMAS linewidths remain narrow. Here, we use this novel methodology in an 27Al (I = 5/2) NMR study of the calcined-dehydrated aluminophosphate AlPO-14 and two forms of as-synthesized AlPO-14, one prepared with isopropylamine (C3H7NH2) as the template molecule and one with piperidine (C5H10NH).

Nitrogen-14 NMR spectroscopy using residual dipolar splittings in solids.

It is shown that nuclear magnetic resonance (NMR) spectra of nitrogen-14 (spin I = 1) can be obtained by indirect detection in powders spinning at the magic angle (MAS). The method relies on the transfer of coherence from a neighboring nucleus with S = 1/2, such as carbon-13, to single- or double-quantum transitions of nitrogen-14 nuclei. The transfer of coherence occurs through second-order quadrupole-dipole cross terms, also known as residual dipolar splittings.

Quadrupolar transfer pathways.

A set of graphical conventions called quadrupolar transfer pathways is proposed to describe a wide range of experiments designed for the study of quadrupolar nuclei with spin quantum numbers I=1, 3/2, 2, 5/2, etc. These pathways, which inter alea allow one to appreciate the distinction between quadrupolar and Zeeman echoes, represent a generalization of the well-known coherence transfer pathways. Quadrupolar transfer pathways not merely distinguish coherences with different orders -2I < or = p< or = +2I, but allow one to follow the fate of coherences associated with single transitions that have the same coherence order p=m(I)(r)-m(I)(s) but can be distinguished by a satellite order q=(m(I)(r))(2)-(m(I)(s))(2).

Silver complexes of cyclic hexachlorotriphosphazene.

The first solid-state structures of complexed P3N3X6 (X = halogen) are reported for X = Cl. The compounds were obtained from P3N3Cl6 and Ag[Al(OR)4] salts in CH2Cl2/CS2 solution. The very weakly coordinating anion with R = C(CF3)3 led to the salt Ag(P3N3Cl6)2+[Al(OR)4]- (1), but the more strongly coordinating anion with R' = C(CH3)(CF3)2 gave the molecular adduct (P3N3Cl6)AgAl(OR')4 (3).

Slow diffusion by singlet state NMR spectroscopy.

Small diffusion coefficients can be measured by using populations of singlet states that have a relaxation time constant, T(s), which can be much longer than the longitudinal relaxation time, T1. Spatial information can be encoded with pulsed field gradients in the manner of stimulated echo sequences. Singlet states can be excited via double-quantum coherences to enhance the efficiency of phase encoding and decoding.

Separation of quadrupolar and chemical/paramagnetic shift interactions in two-dimensional 2H (I=1) nuclear magnetic resonance spectroscopy.

A novel two-dimensional (2)H (spin I=1) nuclear magnetic resonance technique is introduced for determination of both quadrupole and chemical/paramagnetic shift tensors and their relative orientation. The new method is based upon the well-known quadrupolar-echo experiment and is designed to refocus the quadrupolar interaction at the end of the t(1) evolution period while retaining the modulation introduced by the shift interaction. As a result, a projection of the resulting two-dimensional spectrum onto its F(1) dimension yields a shift anisotropy powder lineshape free from any quadrupolar broadening.

Refocussing of chemical and paramagnetic shift anisotropies in 2H NMR using the quadrupolar-echo experiment.

A simple two-pulse spin-echo experiment is shown to refocus inhomogeneous broadening arising from both chemical and/or paramagnetic shift anisotropy and a first-order I=1 quadrupolar interaction. The method is shown to yield 2H NMR spectra of a paramagnetic solid (CuCl2.2D2O) and of a non-paramagnetic solid (D2C2O4.