Two-Dimensional Infrared Spectroscopy of Antiparallel β-Sheet Secondary Structure

We investigate the sensitivity of femtosecond Fourier transform two-dimensional infrared spectroscopy to protein secondary structure with a study of antiparallel β-sheets. The results show that 2D IR spectroscopy is more sensitive to structural differences between proteins than traditional infrared spectroscopy, providing an observable that allows comparison to quantitative models of protein vibrational spectroscopy. 2D IR correlation spectra of the amide I region of poly-L-lysine, concanavalin A, ribonuclease A, and lysozyme show cross-peaks between the IR-active transitions that are characteristic of amide I couplings for polypeptides in antiparallel hydrogen-bonding registry. For poly-L-lysine, the 2D IR spectrum contains the eight-peak structure expected for two dominant vibrations of an extended, ordered antiparallel β-sheet. In the proteins with antiparallel β-sheets, interference effects between the diagonal and cross-peaks arising from the sheets, combined with diagonally elongated resonances from additional amide transitions, lead to a characteristic “Z”-shaped pattern for the amide I region in the 2D IR spectrum. We discuss in detail how the number of strands in the sheet, the local configurational disorder in the sheet, the delocalization of the vibrational excitation, and the angle between transition dipole moments affect the position, splitting, amplitude, and line shape of the cross-peaks and diagonal peaks.

THE INVESTIGATION OF THE EFFECTS OF RADICAL NECK DISSECTIONS TO THE BRAINSTEM BY BRAINSTEM AUDITORY EVOKED POTENTIALS

IN 33 EARS OF 17 PATIENTS WHO HAVE UNDERGONE UNILATERAL OF BILATERAL NECK DISSECTION

Pseudohypoaldosteronism type 1 and respiratory distress syndrome.

We present a patient born at 31 weeks gestation with respiratory distress syndrome (RDS) which did not respond to surfactant. He also developed hyponatremia, hyperkalemia and dehydration with increased sweat electrolytes despite high levels of serum aldosterone, thus systemic pseudohypoaldosteronism type 1 (PHA-1) diagnosis was made. Systemic PHA-1 is caused by mutations of amiloride-sensitive epithelial sodium channel (ENaC) genes. Because ENaC is a rate-limiting step for sodium absorption by epithelial cells, not only of the renal tubule but also of the lung epithelium, patients with PHA-1 with pulmonary symptoms have sometimes been reported. However, our patient appears to be the second reported human case of both neonatal RDS and PHA-1, and the first description, with increased sweat electrolytes, of a premature baby with systemic PHA-1 and RDS