Voices of the dead: complex nonlinear vocal signals from the larynx of an ultrasonic frog.

Most anurans are highly vocal but their vocalizations are stereotyped and simple with limited repertoire sizes compared with other vocal vertebrates, presumably because of the limited mechanisms for fine vocal motor control. We recently reported that the call of the concaveeared torrent frog (Amolops tormotus Fei) is an exception in its seemingly endless variety, musical warbling quality, extension of call frequency into the ultrasonic range and the prominence of subharmonics, chaos and other nonlinear features. We now show that the major spectral features of its calls, responsible for this frog's vocal diversity, can be generated by forcing pressurized air through the larynx of euthanized males.

Six specific lysine residues are crucial in maintaining the structure and function of soluble manganese stabilizing protein.

When manganese stabilizing protein (MSP) was treated with 0.5 mM N-succinimidyl propionate (NSP), the rebinding ability and oxygen-releasing capabilities of the modified MSP were not altered, in spite of changes of MSP surface Lys residues. Furthermore, far-ultraviolet circular dichroism and intrinsic fluorescence spectra analysis revealed that 0.

Ultrasonic communication in frogs.

Among vertebrates, only microchiropteran bats, cetaceans and some rodents are known to produce and detect ultrasounds (frequencies greater than 20 kHz) for the purpose of communication and/or echolocation, suggesting that this capacity might be restricted to mammals. Amphibians, reptiles and most birds generally have limited hearing capacity, with the ability to detect and produce sounds below approximately 12 kHz. Here we report evidence of ultrasonic communication in an amphibian, the concave-eared torrent frog (Amolops tormotus) from Huangshan Hot Springs, China.

Folding studies of two hydrostatic pressure sensitive proteins.

High hydrostatic pressure combined with various spectroscopies is a powerful technique to study protein folding. An ideal model system for protein folding studies should have the following characteristics. (1) The protein should be sensitive to pressure, so that the protein can be unfolded under mild pressure.

[Progresses in the study on light harvesting pigment protein complexes and reaction centers from purple bacteria].

This review describes the recent progress in understanding of light harvesting complexes and reaction centers from purple bacteria. Emphasis is paid on the structure of two light harvesting complexes, inner or outer, and the mechanism of the transfer of excited energy among relative pigments (Fig.1).

Positive charges on lysine residues of the extrinsic 18 kDa protein are important to its electrostatic interaction with spinach photosystem II membranes.

To determine the contribution of charged amino acids to binding with the photosystem II complex (PSII), the amino or carboxyl groups of the extrinsic 18 kDa protein were modified with N-succinimidyl propionate (NSP) or glycine methyl ester (GME) in the presence of a water-soluble carbodiimide, respectively. Based on isoelectric point shift, 4-10 and 10-14 amino groups were modified in the presence of 2 and 4 mM NSP, respectively. Similarly, 3-4 carboxyl groups were modified by reaction with 100 mM GME.

Acetonitrile-induced unfolding of the photosystem II manganese-stabilizing protein studied by electrospray mass spectrometry.

In this paper an acetonitrile-induced unfolding of the manganese-stabilizing protein (MSP) of photosystem II was discovered. More distinct unfolding states of MSP were identified than previously by using mainly electrospray ionization mass spectrometry (ESI-MS), together with fluorescence spectra and far-UV circular dichroism (CD) at pH 2.0, 6.

[Differences in plant hormone level of cucumber seedlings grown under sulfur or xenon lamp].

The primary mechanism of growth difference of cucumber (Cucumis sativus L.) seedlings cultured under sulfur lamp and xenon lamp in a phytotron was investigated. Compared with cucumber seedlings grown under xenon lamp, those under sulfur lamp were shorter, and the cell number in the middle hypocotyls epidermis and cortex of them were more (Fig.

Pressure equilibrium and jump study on unfolding of 23-kDa protein from spinach photosystem II.

Pressure-induced unfolding of 23-kDa protein from spinach photosystem II has been systematically investigated at various experimental conditions. Thermodynamic equilibrium studies indicate that the protein is very sensitive to pressure. At 20 degrees C and pH 5.

[Fourier transform infrared spectroscopy study on the protein secondary structure of photosystem II reaction center].

A successful study on the secondary structure of the isolated photosystem II (PSII) particles with the Fourier transform infrared spectroscopy is reported in this paper. The beta condensation effect is obviously characterized by infrared absorption spectra. The infrared spectra of both living protein and beta condensed protein samples are measured at room temperature.

[Thermodynamic and kinetic analysis of unfolding of P23k protein isolated from spinach photosystem II].

The unfolding of 23kD (P23k) protein isolated from spinach photosystem II particle was studied by high pressure and fluorescence spectroscopy. The thermal equilibrium study indicated that the protein could be totally unfolded by 180 or 160 MPa at 20 degrees C and 3 degrees C, respectively. The standard free energy and standard volume change of the protein for unfolding at 20 degrees C is 23.

Vocal acrobatics in a Chinese frog, Amolops tormotus.

Although amphibians are highly vocal, they generally emit only a limited number of acoustic communication signals. We report here the extraordinarily rich vocal repertoire of Amolops tormotus, a ranid species in China. These frogs produce countless vocalizations, some of which share features of birdsong or primate calls, e.

The Influence of NBS Modification of 241Trp on the Reconstitution of 33 kD Protein with PS and on the Recovery of Oxygen-evolving Activity.

The extrinsic 33 kD protein of photosystemII(PSII) plays an important role in the stabilizing of manganese cluster and maintaining high oxygen-evolving activity of PSII. In this research, (241)Trp, the only tryptophan in the 33 kD protein, was modified by N-Bromosuccinimide. The pH-dependence of modification suggests that this tryptophan is buried in the hydrophobic interior of the protein.

The Photochemical Change in Photosynthetic Reaction Center of Purple Bacterium with Pheophytin Substitution.

The reaction centers are isolated from chromatophores of Rhodobacter sphaeroides 601 by detergent LDAO, and purified by chromatography on a DEAE-52 cellulose column. In the presence of acetone and an access of free pheophytins (Phes), bacteriopheophytins (Bphes) in reaction centers are replaced by pheophytins at sites H(A) and H(B) when incubated under high temperature. The substituting amounts are about 50% and 71% Bphes in reaction centers with incubation of fifteen and sixty minutes respectively.

The Ultrafast Energy Transfer Process in Purple Bacteria Photosynthetic Reaction Center.

The ultrafast energy transfer process, which takes place in femtosecond time range, in bacterial photosynthetic reaction center RS601 was investigated using femtosecond pump-probe technique with selective excitation. Upon 755 nmexcitation, the excited state of bacteriopheophytin H decayed to bacteriochlorophyll B with a time constant of about 130 fs, while the excited state of B transported the energy to its energy acceptor, the dimeric bacteriochlorophyll P, in about 240 fs with the 800 nm excitation. The internal conversion process between the upper and lower exciton levels of special pair P might exist upon the excitation of 850 nm pulses.

Comparison of Different Effects of Chloroacetates on Electron Transports in PS II and in the Reaction Center of Rb. sphaeroides 601.

Chloroacetates displayed different effects on electron transports in the photosynthetic reaction center of purple bacteria (Rb.sphaeroides 601) and in the photosystem II (PS II) of higher plants. Decays of chlorophyII a fluorescence measured after actinic flashes show that chloroacetates inhibit the electron transport from Q(A)(-) to Q(B) (Q(B)(-)) and the equilibrium between Q(A)(-)Q(B) (Q(B)(-)) and Q(A)Q(B)(-) (Q(B)(2-)), acting on electron transport as well as proton transduction.

Studies on the Stimulating Nature of Uncouplers on the Electron Transport in BBY Particles.

BBY particles, which have kept the physicochemical property of PSII, were shown by transmission electron microscopy to possess no intact thylakoid membranes. The results of measuring 9-AA fluorescence quenching and millisecond Chl alpha delayed light emission proved that BBY particles were also unable to establish proton gradient across the membranes (deltapH) in light. Moreover, uncouplers gramicidin D and NH(4)Cl increased PSII electron transport in BBY particles only at low pH.