Anomalous signal from S atoms in protein crystallographic data from an X-ray free-electron laser

X-ray free-electron lasers (FELs) enable crystallographic data collection using extremely bright femtosecond pulses from microscopic crystals beyond the limitations of conventional radiation damage. This diffraction-before-destruction approach requires a new crystal for each FEL shot and, since the crystals cannot be rotated during the X-ray pulse, data collection requires averaging over many different crystals and a Monte Carlo integration of the diffraction intensities, making the accurate determination of structure factors challenging. To investigate whether sufficient accuracy can be attained for the measurement of anomalous signal, a large data set was collected from lysozyme microcrystals at the newly established `multi-purpose spectroscopy/imaging instrument' of the SPring-8 Ångstrom Compact Free-Electron Laser (SACLA) at RIKEN Harima. Anomalous difference density maps calculated from these data demonstrate that serial femtosecond crystallography using a free-electron laser is sufficiently accurate to measure even the very weak anomalous signal of naturally occurring S atoms in a protein at a photon energy of 7.3 keV.

Triterpene constituents from the stem bark of Pinus luchuensis and their DNA topoisomerase II inhibitory effect

Nine lanostane and serratane-type triterpenes including two unknown compounds were isolated from the stem bark of Pinus luchuensis. These new compounds were characterized as 3-oxolanost-9(11)-ene-24S,25-diol (1) and 29-acetoxy-3beta-methoxyserrat-14-en-21alpha-ol (2) on the basis of spectroscopic evidence. Some of these triterpenes were tested for the inhibitory effect on DNA topoisomerase II activity. Compound 1 showed a slightly less potent inhibitory activity with an IC(50) value of 186 microM.

Skin and epidural recording of spinal somatosensory evoked potentials following median nerve stimulation: correlation between the absence of spinal N13 and impaired pain sense

A clinical lesion study and intraoperative epidural recordings were made to test the origin and clinical significance of the spinal N13 and P13 of somatosensory evoked potentials (SEP) that follow median nerve stimulation. Intraoperatively, the respective peak latencies of spinal P13 and N13 coincided with those of the N1 component of the dorsal cord potential and its phase reversed positivity. On both the ventral and dorsal sides of the cervical epidural space, maximal amplitude was at the C5 vertebral level to which nerve input from the C6 dermatome is the main contributor. The modality of sensory impairment in the hand dermatome was examined in selected patients with cervical lesions, who showed such normal conventional SEP components as Erb N9, far-field P9, P11, P14, N18 and cortical N20, with or without loss of spinal N13. Statistically, the loss of spinal N13 was associated with decrease of pain sensation in the C6 dermatome. This was interpreted as being due to damage to the central grey matter of the cord, including the dorsal horn. Our results suggest the spinal N13 and P13 originate from the same source in the C6 spinal cord segment and that they are good indicators for the detection of centromedullary cervical cord damage.

Generation of auditory brain stem responses (ABRs). III. Effects of lesions of the superior olive, lateral lemniscus and inferior colliculus on the ABR in guinea pig

Auditory brain stem potentials were recorded between the skull (vertex) and a non-cephalic reference in guinea pig before and after making discrete lesions of the auditory pathway in the pons and midbrain. Lesions of the superior olivary complex were accompanied by attenuation of P3 and N3 to contralateral input. Lesions of the lateral lemniscus were accompanied by attenuation of N3 to contralateral input. Lesions of the lateral portion of the pons adjacent to the lateral superior olivary nucleus were accompanied by attenuation of P4 to ipsilateral input. Lesions of the inferior colliculus were without effect on the ABR. These data are interpreted as supporting the hypothesis that each component of the ABR arises from a focal region of the brain stem auditory pathway.

Generation of auditory brain stem responses (ABRs). I. Effects of injection of a local anesthetic (procaine HCI) into the trapezoid body of guinea pigs and cat

Auditory brain stem potentials were recorded between the skull and a non-cephalic reference electrode in anesthetized guinea pigs before and after the injection of a local anesthetic agent (procaine HCI) into the trapezoid body from a ventral approach. All components except P1, N1 and P2 were affected; N2 was delayed; P3 and N3 were lost; P4 was both broadened in duration and shortened in latency; N4 was attenuated in amplitude. All of these changes were temporary and recovery of the components occurred. Identification of the altered components was aided by their latency and amplitude changes as a function of both stimulus intensity and rate. This study implicates the trapezoid body as contributing to the generation of auditory brain stem components beginning with N2.

Generation of auditory brain stem responses (ABRs). II. Effects of surgical section of the trapezoid body on the ABR in guinea pigs and cat

Auditory brain stem potentials were recorded between the skull and a non-cephalic reference electrode in guinea pig and cat before and after midline section of the trapezoid body from a ventral approach. The ABR after complete section was altered: N2 was delayed, P3 and N3 were lost, P4 and N4 were shortened in latency but only N4 was attenuated in amplitude. With partial section of the trapezoid body the amplitude of P3 was linearly related to the extent of the section. Recordings from the surface of the trapezoid body before and after section revealed a loss of activity contralateral to the ear stimulated and a preservation of activity ipsilateral to the section. Binaural interaction in P4 and N4 was attenuated in a linear manner as a function of the extent of trapezoid body section. This study suggests that auditory brain stem structures contralateral to the midline of the trapezoid body generate components N2, P3, N3, N4, whereas auditory structures ipsilateral to the midline generate components P1, N1, P2 and P4.