ABSTRACT
A method for obtaining electrocardiographic potential through thin cloth inserted between the measuring electrodes and the skin of a subject's dorsal surface when lying supine has been proposed. The method is based on capacitive coupling involving the electrode, the cloth, and the skin. Examination of a pilot device which employed the method revealed the following: (1) In spite of the gain attenuation in the high frequency region, the proposed method was considered useful for monitoring electrogardiogram (ECG) for nondiagnostic purpose. (2) The method was able to yield a stable ECG from a subject at rest for at least 7 h, and there was no significant adverse effect of long-term measurement on the quality of the signal obtained. (3) Electrode area was the factor that had most influence on the signal, compared with other factors such as cloth thickness and coupling pressure, but could be reduced to 10 cm2 for heart rate detection. (4) Input capacitance of the device was assumed to be the dominant factor for the gain attenuation in the high frequency region, and should be reduced with a view to diagnostic use. Although there is still room for improvement in terms of practical use, the proposed method appears promising for application to bedding as a noninvasive and awareness-free method for ECG monitoring.
Subject(s)
Electric Capacitance , Electrocardiography, Ambulatory/instrumentation , Electrocardiography, Ambulatory/methods , Electrodes , Supine Position , Adult , Equipment Design , Equipment Failure Analysis , Humans , Male , Reproducibility of Results , Sensitivity and Specificity , TextilesABSTRACT
Bacterial 3alpha-hydroxysteroid dehydrogenase, which belongs to a short-chain dehydrogenase/reductase family and forms a dimer composed of two 26-kDa subunits, catalyzes the oxidoreduction of hydroxysteroids in a coenzyme-dependent manner. This enzyme also catalyzes the oxidoreduction of nonsteroid compounds that play an important role in xenobiotic metabolism of bacteria. We performed an x-ray analysis on the crystal of Ps3alphaHSD, the enzyme from Pseudomonas sp. B-0831 complexed with NADH. The resulting crystal structure at 1.8A resolution showed that Ps3alphaHSD exists as a structural heterodimer composed of apo- and holo-subunits. A distinct structural difference between them was found in the 185-207-amino acid region, where the structure in the apo-subunit is disordered whereas that in the holo-subunit consists of two alpha-helices. This fact proved that the NADH binding allows the helical structures to form the substrate binding pocket even in the absence of the substrate, although the region corresponds to the so-called "substrate-binding loop." The induction of alpha-helices in solution by the coenzyme binding was also confirmed by the CD experiment. In addition, the CD experiment revealed that the helix-inducing ability of NADH is stronger than that of NAD. We discuss the negative cooperativity for the coenzyme binding, which is caused by the effect of the structural change transferred between the subunits of the heterodimer.
Subject(s)
3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)/chemistry , Pseudomonas/enzymology , Circular Dichroism , Dimerization , Electrons , Hydrogen Bonding , Models, Molecular , NAD/chemistry , Protein Binding , Protein Conformation , Protein Folding , Protein Structure, Secondary , Protein Structure, Tertiary , X-Ray DiffractionABSTRACT
The NAD(P)(+)-dependent enzyme 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) catalyzes the reversible interconversion of hydroxyl and oxo groups at position 3 of the steroid nucleus. The complex of NADH and 3alpha-HSD from Pseudomonas sp. B-0831 was crystallized by the hanging-drop vapour-diffusion method. Refinement of crystallization conditions with microseeding improved the quality of the X-ray diffraction data to a resolution of 1.8 A. The crystals belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 62.46, b = 82.25, c = 86.57 A, and contained two molecules, reflecting dimer formation of 3alpha-HSD, in the asymmetric unit.
Subject(s)
3-Hydroxysteroid Dehydrogenases/chemistry , 3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)/chemistry , NAD/chemistry , Pseudomonas/enzymology , Bacterial Proteins/chemistry , Crystallization , Dimerization , X-Ray DiffractionABSTRACT
A new system has been developed for obtaining electrographic potential through thin underwear inserted between the measuring electrodes and the skin of a neonate or an infant when lying supine. The system is based on capacitive coupling involving the electrode, the underwear, and the skin. Validation of the system revealed the following: (1) the signal detected using the system displayed a periodic waveform synchronized with the simultaneously recorded ECG, even when thin underwear was inserted between the electrode and the skin, (2) the gain of the system when the cloth was inserted decreased as the frequency increased. The present system appears promising for application to bedding as a non-invasive and awareness-free method for ECG monitoring of neonates or infants. However, there is still room for improvement in terms of its practical use, because the high-frequency component of the signal was depressed in comparison with the reference ECG.
