Microstructural characterization data of as received IG-110, 2114 and ETU-10 nuclear graphite grades and oxidation characterization data of IG-110.

This manuscript provides optical microscopy, scanning electron microscopy, and transmission electron microscopy micrographs that show the microstructure of three superfine nuclear graphite grades IG-110, 2114 and ETU-10. This collection of microstructural data showcases the microstructure of these materials and helps to differentiate the most important features or phases of these graphite grades. In particular, the microstructural data illustrate the filler and binder morphology of these grades. Moreover, samples of as-received and oxidized IG-110 were characterized via optical microscopy and x-ray computed tomography. The microstructural data of oxidized IG-110 shows the porosity generated by oxidation experiments. These micrographs and data provide a unique insight into the microstructural features and oxidation effects in nuclear graphite and can be used to perform quantitative porosity analysis. This collection of microstructural data complements the modeling and characterization described in the associated manuscript, "Using porous random fields to predict the elastic modulus of unoxidized and oxidized superfine graphite (Arregui-Mena et al., 2022)."

Lipophilic 99mTc-nitride radiopharmaceuticals as potential myocardial imaging agents.

Monocationic 99mTc-nitrido complexes of a variety of diphosphine ligands have been prepared and the in vivo distribution of such cations has been examined in Sprague-Dawley rats. These complexes show initially high myocardial uptake with subsequent wash-out in this animal model. The lack of myocardial retention can be attributed to the facile in vivo reduction of these cations.

Identification of the 1H resonances of valine and leucine residues in dihydrofolate reductase by using a combination of selective deuteration and two-dimensional correlation spectroscopy.

Lactobacillus casei dihydrofolate reductase (Mr 18 500) contains 16 valine and 14 leucine residues. By comparing the 2D COSY NMR spectra of normal and [gamma-2H6]valine enzyme we have been able to identify all 60 methyl resonances from these residues, and to connect the pairs arising from the same residue. This pairing of the methyl resonances was aided by the examination of the 2D RELAY spectrum which also allowed the C alpha H resonances (and hence the complete spin systems) of 14 of the valine residues to be identified. The combination of selective deuteration with 2D NMR techniques is shown to be a powerful general method for resolving 1H resonances in the complex spectra of proteins and for assigning them to amino-acid type.

The combined use of selective deuteration and double resonance experiments in assigning the 1H resonances of valine and tyrosine residues of dihydrofolate reductase.

Selective deuteration is a general solution to the resolution problem which limits the application of double resonance experiments to the assignment of the 1H NMR spectra of proteins. Spin-decoupling and NOE experiments have been carried out on Lactobacillus casei dihydrofolate reductase and on selectively deuterated derivatives of the enzyme containing either [gamma-2H6]Val or [alpha, delta 2, epsilon 1-2H3]His, [alpha, delta 1, delta 2, epsilon 1, epsilon 2, zeta-2H6]Phe, [alpha, delta 1, epsilon 3, zeta 2, zeta 3, eta 2-2H6]Trp and [alpha, epsilon 1, epsilon 2-2H3]Tyr. When combined with ring-current shift calculations based on the crystal structure of the enzyme, these experiments allow us to assign 1H resonances of Val 61, Val 115, Tyr 46 and Tyr 68.

Proton nuclear magnetic resonance studies of the effects of ligand binding on tryptophan residues of selectively deuterated dihydrofolate reductase from Lactobacillus casei.

We have prepared a selectively deuterated dihydrofolate reductase in which all the aromatic protons except the C(2) protons of tryptophan have been replaced by deuterium and have examined the 1H NMR spectra of its complexes with folate, trimethoprim, methotrexate, NADP+, and NADPH. One of the four Trp C(2)-proton resonance signals (signal P at 3.66 ppm from dioxane) has been assigned to Trp-21 by examining the NMR spectrum of a selectively deuterated N-bromosuccinimide-modified dihydrofolate reductase. This signal is not perturbed by NADPH, indicating that the coenzyme is not binding close to the 2 position of Trp-21. This contrasts markedly with the 19F shift (2.7 ppm) observed for the 19F signal of Trp-21 in the NADPH complex with the 6-fluorotryptophan-labeled enzyme. In fact the crystal structure of the enzyme . methotrexate . NADPH shows that the carboxamide group of the reduced nicotinamide ring is near to the 6 position of Trp-21 but remote from its 2 position. The nonadditivity of the 1H chemical-shift contributions for signals tentatively assigned to Trp-5 and -133 indicates that these residues are influenced by ligand-induced conformational changes.