Publisher Summary The vibrational spectrum of a molecule is determined by its three-dimensional structure and its vibrational force field. An analysis of this (usually infrared (IR) and Raman) spectrum can therefore provide information on the structure and on intramolecular and intermolecular interactions. The more probing the analysis, the more detailed is the information that can be obtained. Detailed analyses of the vibrational spectra of macromolecules, however, have provided a deeper understanding of structure and interactions in these systems. An important advance in this direction for proteins came with the determination of the normal modes of vibration of the peptide group in N-methylacetamide, and the characterization of several specific amide vibrations in polypeptide systems. Extensive use has been made of spectra-structure correlations based on some of these amide modes, including attempts to determine secondary structure composition in proteins. Polypeptide molecules exhibit many more vibrational frequencies than the amide modes. Over the years, some normal-mode calculations have provided greater insight into the spectra of particular molecules. However, these have often been based on approximate structures or have employed limited force fields. These force fields can now serve as a basis for detailed analyses of spectral and structural questions in other polypeptide molecules. The aim of this chapter is to present these recent developments in the vibrational spectroscopy of peptides, polypeptides, and proteins.

Vibrational spectroscopy and conformation of peptides, polypeptides, and proteins.

Background An accurate, noninvasive technique for the diagnosis of coronary disease would be an important advance. We investigated the accuracy of coronary magnetic resonance angiography among patients with suspected coronary disease in a prospective, multicenter study. Methods Coronary magnetic resonance angiography was performed during free breathing in 109 patients before elective x-ray coronary angiography, and the results of the two diagnostic procedures were compared. Results A total of 636 of 759 proximal and middle segments of coronary arteries (84 percent) were interpretable on magnetic resonance angiography. In these segments, 78 (83 percent) of 94 clinically significant lesions (those with a ≥50 percent reduction in diameter on x-ray angiography) were also detected by magnetic resonance angiography. Overall, coronary magnetic resonance angiography had an accuracy of 72 percent (95 percent confidence interval, 63 to 81 percent) in diagnosing coronary artery disease. The sensitivity, specificity,...

Coronary Magnetic Resonance Angiography for the Detection of Coronary Stenoses

A flow-independent method for imaging the coronary arteries within a breath-hold on a standard whole-body MR imager was developed. The technique is based on interleaved spiral k-space scanning and forms a cardiac-gated image in 20 heartbeats. The spiral readouts have good flow properties and generate minimal flow artifacts. The oblique slices are positioned so that the arteries are in the plane and so that the chamber blood does not obscure the arteries. Fat suppression by a spectral-spatial pulse improves the visualization of the arteries.© 1992 Academic Press,Inc.

Fast spiral coronary artery imaging

Background and Methods This study was designed to assess the safety and reliability of new noninvasive imaging methods as compared with aortography in the diagnosis of dissection of the thoracic aorta. One hundred ten patients with clinically suspected aortic dissection followed a diagnostic protocol that included transthoracic and transesophageal color-flow Doppler echocardiography (TTE and TEE), contrast-enhanced x-ray computed tomography (CT), and magnetic resonance imaging (MRI). Imaging results were compared in a blinded fashion and validated independently against intraoperative findings in 62 patients, autopsy findings in 7, and the results of contrast angiography in 64. Results The sensitivities of MRI, TEE and x-ray CT for detecting dissection were similar, at 98.3, 97.7, and 93.8 percent, respectively; TTE had a sensitivity of only 59.3 percent (P<0.005). The specificities of both TTE (83.0 percent) and TEE (76.9 percent) were lower than those of x-ray CT (87.1 percent) and MRI (97.8 percent; P<0...

The diagnosis of thoracic aortic dissection by noninvasive imaging procedures.

The importance of A TP as the main source of chemical energy in living matter and its involve­ ment in cellular processes has long been recog­ nized. The primary mechanism whereby higher or­ ganisms, including humans, generate ATP is through mitochondrial oxidative phosphorylation. For the majority of organs, the main metabolic fuel is glucose, which in the presence of oxygen under­ goes complete combustion to CO2 and H20: C6H1206 + 602 � 602 + 6H20 + energy ( 1) The free energy (.:lG) liberated in this exergonic re­ action is partially trapped as ATP in two consecu­ tive processes: glycolysis (cytosol) and oxidative phosphorylation (mitochondria). The first produces 2 mol of ATP per mol of glucose, and the second 36 mol of ATP per mol of glucose. In the latter case, 6 mol of ATP are contributed from the oxidation of 2 mol of NADH generated in the cytosol during gly­ colysis and transferred into the mitochondria indi­ rectly through various \"shuttle\" systems. (In the a-glycerophosphate shuttle, the yield of ATP per NADH is reduced from 3 to 2 because the relevant mitochondrial dehydrogenase is a flavoprotein­ linked enzyme). Thus, oxidative phosphorylation yields 1718 times as much useful energy in the form of ATP as can be obtained from the same amount of glucose by glycolysis alone. It is there­ fore not surprising that limitation of O2 supply pro­ duces very damaging effects on cellular function. The brain is one of the organs that is particularly sensitive to lack of oxygen and in humans at rest is responsible for 20% of total O2 consumption al­ though it accounts for only 2% of the body weight. The role of energy in the maintenance of central

https://journals.sagepub.com/doi/pdf/10.1038/jcbfm.1989.2

ATP and brain function

The conformation of gramicidin A.

A sensitive and specific blood test for cancer has long been sought. The water-suppressed proton nuclear magnetic resonance (NMR) spectrum of plasma is dominated by the resonances of plasma lipoprotein lipids. We measured the mean line widths of the methyl and methylene resonances, which were found to be correlated with the presence or absence of malignant tumors. Values for the average line width were lower in patients with cancer. We analyzed plasma from 331 people (normal controls, patients with malignant and benign tumors, patients without tumors, and pregnant patients); NMR analysis and measurement of line widths were blinded to diagnosis or patient group. The mean line width for 44 normal controls (+/- SD) was 39.5 +/- 1.6 Hz. For 81 patients with untreated cancer, demonstrated by biopsy, the line width was 29.9 +/- 2.5 Hz. Patients with malignant tumors were reliably distinguished from normal controls by this method (P less than 0.0001), and differed from patients with diseases that did not involve tumors (line width, 36.1 +/- 2.6 Hz; P less than 0.0001). Patients with benign tumors (e.g., those of the breast, ovary, uterus, and colon) had line widths of 36.7 +/- 2.0 Hz and were different from those with malignant tumors (P less than 0.0001). However, pregnant patients and those with benign prostatic hyperplasia had line widths consistent with the presence of malignant tumors. The narrowing of lipoprotein-lipid resonances with cancer is consistent with the response of a host to tumor growth. We conclude that these preliminary results demonstrate that water-suppressed proton NMR spectroscopy is a potentially valuable approach to the detection of cancer and the monitoring of therapy.

Detection of malignant tumors. Water-suppressed proton nuclear magnetic resonance spectroscopy of plasma.

Six patients who had recently undergone selective coronary and left ventricular angiography were prospectively examined with MR to show the aortic root and proximal coronary arteries. The examinations were performed with a superconductive 1.5-T instrument with spin-echo sequences and ECG-gated multiple slices of 5-mm thickness. The location and plane direction of the scan were guided by findings on initial coronary MR scout scans and by a review of the angiograms. In four of the six patients both coronary orifices and the proximal centimeters of both coronary arteries were identified. In the remaining two, only the left proximal coronary artery was seen. Although segments of more peripherally located portions of the main coronary arteries and branches were detectable, a prospective and conclusive identification without knowledge of the angiographic anatomy would have been extremely difficult. Differential diagnostic problems, such as erroneous interpretation of pericardial recesses and coronary veins, were observed. Unsuccessful demonstration of the right coronary artery orifice in two cases coincided with more peripherally located occlusion of the vessels on the angiogram. MR with spin-echo sequences appears to be unsatisfactory for diagnosis of coronary arteriosclerotic disease, but it may be useful in other conditions that result in significant coronary dilatation, such as fistulae and aneurysms.

https://www.ajronline.org/doi/pdfplus/10.2214/ajr.148.4.665

MR imaging of the aortic root and proximal coronary arteries.

Aqueous shift reagents for high-resolution cationic nuclear magnetic resonance. III: Dy(TTHA)3-, Tm(TTHA)3-, and Tm(PPP)27-

Levels of the high-energy phosphate-containing compounds, ATP and creatine phosphate, and of inorganic phosphate (Pi) were measured as a function of position in the cardiac cycle. Measurements were made on isolated, perfused, working rat hearts through the use of gated 31P nuclear magnetic resonance spectroscopy. Levels of ATP and creatine phosphate were found to vary during the cardiac cycle and were maximal at minimal aortic pressure and minimal at maximal aortic pressure. Pi varied inversely with the high-energy phosphates.

Eric T. Fossel

Papers

The conformation of gramicidin A.

Detection of malignant tumors. Water-suppressed proton nuclear magnetic resonance spectroscopy of plasma.

MR imaging of the aortic root and proximal coronary arteries.

Aqueous shift reagents for high-resolution cationic nuclear magnetic resonance. III: Dy(TTHA)3-, Tm(TTHA)3-, and Tm(PPP)27-

Measurement of changes in high-energy phosphates in the cardiac cycle using gated 31P nuclear magnetic renonance.