The spin-spin, T2, and spin-lattice, T1, relaxation times and the magnetization of protons were measured in human enamel. The proton free induction decay was analyzed into solid-like interstitial water, enamel apatite, and semiliquid-like water components. The solid-like interstitial water was evaluated to be approximately 5 wt% and the semiliquid-like water to be approximately 1 to 2%. Neither in wet nor in dry natural enamel does the solid water exchange upon deuteration nor can it be extracted in vacuum. The semiliquid natural water, which is in the closed pores of the structure in the two samples above also remains unexchanged upon an 8 hr deuteration and cannot be extracted in a vacuum. With the lineshape-relaxation correlation NMR the free induction decays from heads and tails of the enamel rods were resolved. The solid-like water with T2 of approximately 14 microseconds and the apatite with a T2 of approximately 61 microseconds have T2's too short to be observed in an NMR zeugmatogram. Therefore only the semiliquid water component having an apparent T*2 of about 240 microseconds would contribute to the NMR image of human enamel. Since the relative intensity of this proton magnetization component in tooth is quite small the NMR image of tooth would show primarily the dentin and liquids within the tooth and on its surface.

ABSTRACT. Cardiac effects of the neuropeptide pituitaryAbbreviations adenylate cyclase activating p o l y p e p t i d e -(~~~i~) have not previously been reported. W e investigated the influence of PACAP, vasoactive intestinal polypeptide (68% homology with PACAP) and the B-adrenergic receptor agonist isoproterenol on contractile function and coronary vascular tone in isolated piglet hearts (1 to 5 d of age). Paced (180 beatslmin) isovolumically beating hearts underwent retrograde aortic perfusion a t constant coronary flow (approximately 3 mL. min-' . g-') with an erythrocyte-enriched PACAP, pituitary adenylate cyclase activating polypeptide VIP, vasoactive intestinal polypeptide ISP, isoproterenol IBMX, isobutylmethylxanthine dP/dt,,, maximum rate of change of systolic pressure with respect to time (+), positive (-), negative (hematocrit 15 to 20%)~solution ( 3 7 "~) . ~g o n i s t s were injected into the aortic root of hearts, and the positive (+) and negative (-) changes in maximum rate of change of systolic pressure with respect to time (dP/dtma,) and in PACAP is a newly discovered neuropcptide isolated from the coronary perfusion pressure (that reflected alterations in ovine hypothalamus (1). PACAP is present in two forms: one vascular tone) were measured. PACAP (n = 8,O.l and 0.5 with 27 and the other with 38 N-terminal amino acid residues nmol) increased (+) dP/dt,, from 944 + 59 to 1519 f 206 (2). PACAP has a 68% sequence homology with VIP and appears mm ~g / s and from 867 2 40 to 2010 +: 226 mm ~g / s ( p to be more potent than VIP in stimulating adenylate cyclase in < 0.05); increased (-1 dpldt,, from 11 14 41 to 14-39 + pituitary cells (2). PACAP also has been shown to increase cAMP 9 5 mm ~g and from 999 f 37 to 1668 + 145 mm H~/ S levels in the human neuroblastoma cell line NB-OK (3), the rat ( p < 0.05); and decreased perfusion pressure from 61.4 2 pancreatic acinar cell line AR 4-25 (4), and rat liver cell mem-3.1 to 48.9 2 2.3 mm 1 1~ and from 60.5 + 2.4 to 43.9 branes ( 5 ) . Moreover, high affinity binding sites for PACAP have 2.3 mm H~ (p < 0.05), respectively. comparison, vase-been identified in several organ systems, including the rat lung active intestinal polypeptide (n = 6, 0.1 and 0.5 nmol) (6) and h m a n brain (7). increased (+) dP/dtmn, from 767 +. 53 to 806 + 37 mm Hg/ The ~h~s i o l o g i c role of PACAP has not been elucidated, and from 829 2 94 to 942 8 5 mm ~g /~ (NS); increased although it has been suggested that this peptide may be involved (-) dp/dtma, from 883 2 73 to 926 45 ,,,,,, ~g /~ and in the regulation of vascular smooth muscle tone, in addition to from 923 + 8 2 to 1054 f 78 mm Hg/s (NS); and decreased its presumed role as a hypothalamic, hypophysiotropic hormone perfusion pressure from 57.9 + 4.9 to 50.0 +. 3.6 mm H~ (8 VIP, have been demonstrated in the myocardium and coronary duced positive inotropic, luisitropic, and coronary vasodil-arteries of several adult species (12). The present study, therefore, effects in piglet which may make a was undertaken to inv...

In wet hen egg white lysozyme (HEWL), the molecular dynamics at the lysozyme–water interface was studied using a proton NMR line-shape-relaxation correlation approach that employed selective inversion of the proton magnetization. The intrinsic lysozyme proton spin-lattice relaxation rate, the intrinsic water proton spin-lattice relaxation rate, and the lysozyme proton – water proton cross-relaxation rate were determined. The lysozyme proton – water proton intermolecular interaction couples these protons and contributes to spin-lattice relaxation as well. The results suggest that a minimum of three different correlation times are needed to characterize the water molecule dynamics in wet HEWL.

Measurements of absolute proton signal intensities, free induction decays, spin-spin relaxation times, and local fields in the rotating frame in natural and fully deuterated mouse muscle at five temperatures in the range 293-170 K are reported. The analysis is carried out at three time windows on the free induction decay. The contribution to the magnetization from protons on large molecules and water are analyzed.

Proton nuclear magnetic resonance relaxation investigations of water dynamics in hydrated protein powders have the serious drawback that protein-water intermolecular dipolar interactions make the unambiguous interpretation of the results difficult. To circumvent this difficulty, deuteron spin-lattice and spin-spin relaxation times in lysozyme powder hydrated with deuterium oxide were measured as a function of temperature and at two frequencies. Although the deuteron relaxation results are compatible with a water molecule dynamics model based on either a bimodal distribution of correlation times or anisotropic motion, a comparison of the present results with proton data suggests than an anisotropic motion model is more likely to provide a reasonable description of the water molecule motion. An analysis based on an anisotropic motion model that uses two correlation times to characterize the motion shows that most of the water molecules rotate about their twofold axis of symmetry at a rate that is only approximately 100 times smaller than the rate of isotropic diffusion in the bulk liquid. The reorientation of the twofold axis of symmetry itself is characterized by a correlation time of approximately 10(-7) s.