V. A. Chupin

Structural insights into the proton pumping by unusual proteorhodopsin from nonmarine bacteria

Light-driven proton pumps are present in many organisms. Here, we present a high-resolution structure of a proteorhodopsin from a permafrost bacterium, Exiguobacterium sibiricum rhodopsin (ESR). Contrary to the proton pumps of known structure, ESR possesses three unique features. First, ESRs proton donor is a lysine side chain that is situated very close to the bulk solvent. Second, the α-helical structure in the middle of the helix F is replaced by 310- and π-helix–like elements that are stabilized by the Trp-154 and Asn-224 side chains. This feature is characteristic for the proteorhodopsin family of proteins. Third, the proton release region is connected to the bulk solvent by a chain of water molecules already in the ground state. Despite these peculiarities, the positions of water molecule and amino acid side chains in the immediate Schiff base vicinity are very well conserved. These features make ESR a very unusual proton pump. The presented structure sheds light on the large family of proteorhodopsins, for which structural information was not available previously.

Internal marine waves and atmospheric depressions

This work describes the results of processing experimental data during synchronous registration of the crust deformations and oscillations of atmospheric and hydrospheric pressures. It was found that internal marine waves with a frequency range from 5 to 20 min are mainly generated by atmospheric disturbances, whose variations are absolutely identical to those of hydrospheric pressure in the shelf zone of the Sea of Japan.

The feasibility of laser strainmeters for sea floor diagnostics

Based on experimental works devoted to study of a lowfrequency (central frequency is 33 Hz) emitter and shorebased laser strainmeter for investigation of the Earths crust structure and definition of the main elastic properties of rocks on emitter-receiver paths, it has been shown that application of these instruments with an increase in the power of receivers and a tunable central frequency of radiation is a promising feature due to the broad operational frequency range and high sensitivity of the laser strainmeters. As is known (1-3), in the low frequency region, seismoacoustic surface waves become the dominating mechanism of acoustic energy transport in the shelf zone, and this feature can be used during experiments on study of the crustal structure within shelf zones of different seas. Since the frequencies of signals emitted by lowfrequency hydroacoustic emitters are about 20-35 Hz (i.e., wavelengths in water are about 75- 40 m, and about 150-100 m in the solid medium at an elastic wave velocity of about 3000 m/s), the depth of the signal penetration into the Earths crust is signifi� cant. All soundings of sediments or water medium are implemented using the technique of signal investiga� tion at the chosen frequencies and their reception by various, preferably broadband, receivers. Broadband receiver systems are used in order to avoid probable distortion of the received information. The time inter� vals between emission and reception time must be measured very accurately in order to obtain the appro� priate thicknesses of studied layers, but this cannot be done if harmonic or pulsed signals are used. In the studies of this kind, complex, phaseshift signals (M� sequences) are preferred; their application in hydroa� coustic and seismoacoustic tomography and inversion studies allows specialists to define the arrival times with a high accuracy. Additionally, signal attenuation does not affect the processing result significantly, because the main processing stage is not related to spectraltemporal investigation of the signal behavior, but to convolution of the received and emitted signals. This peculiarity makes this technique feasible even with significant noise, whose amplitude can exceed that of the received hydroacoustic or seismoacoustic signals.

Recording of deformation anomaly of a tsunamigenous earthquake using a laser strainmeter

A deformation anomaly with a size of approximately 59.3 µ m caused by a tsunamigenous earthquake on December 26, 2004, was detected using a 52.5-m horizontal laser strainmeter of the unequal arm type set in Primorskii Krai of Russia. It was possible to predict a powerful tsunami wave based on the size of the deformation anomaly, which reached the strainmeter location region from the earthquake epicenter in 19 min 54 s.

Loading effect of sea level variations on the Earth’s crust

Different experimental studies in any of the com ponents of the atmosphere–hydrosphere–lithosphere transitional zone should take into account the possible erroneous interpretation of the results obtained due to lack of information about the studied processes in other geospheres. While the influence of atmospheric processes on processes in the hydrosphere is more or less well studied, the loading effect of hydrospheric processes on the level of crustal deformations is unknown, because of the uncertain structure of the Earth’s crust and because the way in which hydro spheric processes affect the Earth’s crust is almost unknown. Of course, it is known that wind driven sea waves generate microseisms of the respective periods in the crust during interacting between waves and the seafloor—it was noted as early as the 1960s by K. Has selmann [1].

A hydrophysical laser-interference complex

An upgraded laser measurer of hydrosphere pressure variations is described. By mounting new pressure and temperature sensors and optimizing the design of the submersible instrument, it has become possible to considerably increase the measurement accuracy of amplitude−frequency characteristic describing variations in the pressure, aqueous medium temperature, and wave amplitudes at the sea surface in the infrasonic and audio ranges and to correct plotted time dependences of the pressure variations in view of the variations in the interferometer and outboard water temperatures. For long-term (up to 40 h) self-contained operation of the complex to be guaranteed, a versatile floating container has been developed. This container is equipped with high-power batteries and data acquisition systems receiving information from the sensors and can be joined to a hermetically sealed connector of the complex instead of the cable line used for communication between the complex and coast equipment.

Dynamics of wind waves during propagation over a shelf of decreasing depth

A laser meter of pressure variation in the hydro sphere [1, 2] and a mobile laser meter of pressure vari ations in the hydrosphere [3] were used as the laser interference receiving systems. They were included in the laser interference hardware–software complex [4, 5] deployed at different depths in Vityaz Bay of Peter the Great Gulf in the Sea of Japan along the direction of wind wave propagation (Fig. 1). The laser meter of pressure variation in the hydrosphere was deployed at a depth of 11.8 m, and the mobile laser meter of pres sure variations in the hydrosphere was set at a depth of 4.5 m. The distance between the instruments was 96 m. The information from these laser interference systems was transmitted by cable lines to the coastal station and recorded in the data bank with a sampling fre quency of 500 Hz. Later, these experimental data were processed using a specially developed programming package software Deformograf, which applied differ ent methods of obtaining spectral and statistical esti mates.

The Nature of the “Voice of the Sea”

Strong vibrations of the Earth’s crust in the frequency range of 7–9 Hz, referred to as the “voice of the sea,” have been recorded in the course of processing synchronous experimental data obtained during recording of variations in the deformation of the Earth’s crust using a shore laser strainmeter, atmosphere pressure variations using a laser nanobarograph, and hydrosphere pressure variations using a laser meter for hydrospheric pressure and wind velocity variations. The nature of these vibrations and their transformation to adjacent geospheres have been discussed.

Particulars of a transmitted acoustic signal at the shelf of decreasing depth

The paper analyzes the experimental data obtained in a comprehensive experiment aimed at identifying the regularities of transmitted hydroacoustic signal transformations at the shelf of decreasing depth. The 33 Hz harmonic hydroacoustic signals were generated at the shelf of the Sea of Japan by a low-frequency source. Distribution of the transmitted energy at vertical sounding from the surface to the bottom was studied at different shelf points with Bruel & Kjaer 8104 hydrophone. At the shore, the transformed seismo-acoustic signals were received by a 52.5 m shore laser strainmeter. The experiments showed that about 22% of the transmitted energy was transformed into the energy of hydroacoustic waves propagating in the water. About 72% of hydroacoustic wave energy, in turn, was transformed into the energy of R-waves, which were registered by the shore laser strainmeter. Other regularities of hydroacoustic signals distribution with 33 Hz frequency over the V-shaped shelf are identified.

A hydroacoustic system that radiates at frequencies of 19−26 Hz

A radiating hydroacoustic system intended to generate harmonic and phase-shifted hydroacoustic signals in the frequency band of 1 Hz with a center frequency in the range of 19−26 Hz is described. The maximum change in the radiator volume may be as large as 0.0123 m3, which corresponds to a radiated acoustic power of 1000 W at a frequency of 20 Hz in the boundless water space. The prospects of using the system for carrying out research are demonstrated via the results of its testing on the shelf of the Sea of Japan.