SYNTHESIS OF PEPTIDES AND AMINO ACIDS _ Previous researches by Professor I.E. El’piner and his colleagues at the Russian Institute of Biophysics have shown that under the action of an ultrasonic field, a number of substances such as ammonia, prussic acid, aldehydes and amino acids could be synthesised. In a recent paper, Professor El’piner provides data which show that peptides, heterocyclic compounds with a nitrogen atom in the cycle (imidazole), and a number of amino acids can be synthesised in an ultrasonic field under certain conditions. Accurate data on the synthesis of peptides were obtained as the result of activating for 2 hours a 5% aqueous solution of ethylene glycol and 0.25% hydroxylamine in the presence of argon in an ultrasonic field of frequency ‘750kHz and power intensity lOW/cmz. Chromatographs of the ammonia fraction were obtained after passing the activated solution through an ion exhange resin.
it was bonded with In film onto a face of a fused quartz delay rod. A Y-cut quartz transducer with a fundamental frequency of 20MHz was bonded to another face of the delay rod and was connected to a receiver. The oscillator was driven by a dc pulse of 1. 5~s at 5pps. When the applied voltage was increased to 4kV/cm, the diode broke into coherent oscillation at 140MHz. An ultrasonic signal of 140MHz was then detected by the transducer, delayed by 4~~s(corresponding to the delay time of shear waves in a 15mm quartz rod). The ultrasonic signal was observed only when the Gunn diode was oscillating. The current/voltage characteristics of the diode and the amplitude of the corresponding signal are shown in Fig 10.
The spots appearing on the chromatographs were examined and if the duration of activation was increased to 6 hours, spots identifiable as alamines, glycocoll and glutamic acid were seen. A persistent spot was identified as being characteristic of comparatively large peptides. There are indications that the synthesis of peptides is probably determined by the formation of prussic acid, the synthesis of which also takes place in an ultrasonic field as previously discovered. The synthesis of peptides can also be brought about by the activation of amino acids and this has been confirmed to some extent by Professor El’piner’s work on the synthesis of amino acid hydroxamates and anhydrides in an ultrasonic field. The formation of imidazole also occurs in an ultrasonic wave field, the initial products for the formation being formaldehyde and ammonium nitrate in aqueous solution. Imidazole was detected chromatographically after such a solution was activated for 4 hours in the presence of argon at 750kHz with an intensity of 10W/cm2. Other substances such as glycocoll were also detected. Professor El’piner concludes that the initiation of the chemical processes studied takes place in the gaseous phase (cavitation bubbles) where the argon ‘catalyses’ the disintegration reaction of the water molecules forming free hydroxyl radicals, which are highly reactive in nature. Further development of the chemical processes is assisted by the fact that they take place at the boundary between the cavitation bubbles and the liquid. Gas bubbles are being continuously formed throughout the entire activated region of the aqueous solution. Professor I. E. El’piner, Institute of Biophysics, The Academy of Sciences, Profsoyuznaya 7, Moscow V-133, USSR
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200 Bias
LOO voltage
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600
of GaAs diode[v]
Fig 10 Current/voltage characteristics of the Gunn oscillator and the corresponding ultrasonic amplitude
The Japanese workers suggest that the Gunn oscillator may be one of the more promising generators of high frequency coherent ultrasonic waves, especially microwave ultrasound, since Gunn oscillation in the microwave region is possible and the frequency of the ultrasound is independent of the mechanical eigenfrequency of the oscillator. H. Hayakawa et al, Electrotechnical Tanashi, Tokyo, Japan
Laboratory, Mukodai.
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ULTRASOUND FROM A GUNN OSCILLATOR -The production of coherent ultrasonic waves with a Gunn oscillator has been reported by the Electrochemical Laboratory in Tokyo. Several attempts to find the effect have been made previously, but a recent report in ‘Applied Physics Letters’ by H. Hayakawa et al is the first account of successful detection. In 1963, John Gunn of IBM found that electric fields produced microwave oscillations in several types of semiconducting materials. It was known that the electric field produced a strain in the crystal lattice, and a number of physicists noted that this strain should produce acoustic waves by the piezoelectric effect. In the recent Japanese work, Gunn diodes were prepared from a slice of n-GaAs with resistivity and mobility of 1212cm and 7000cmz/V/s, respectively. Ohmic contacts were obtained by evaporating Au-Ge -Ni alloy on the [ 1101 flat polished faces. The slice was then cut into small diodes of lmm2 X 0. 7mm. The oscillation frequency of the Gunn diode was 140MHz and
DEMONSTRATION OF ULTRASONIC IMAGING At the Welding Institute in London, Mr D. 0. Sproule recently demonstrated an ultrasonic imaging device that is claimed to have several advantages over conventional methods. The device consists of a small hand-held immersion tank in which a variable-angle probe scans the object under examination. A B-scope display indicates the angle of refraction of the ultra-. sound which is computed by a mechanism using a mechanical linkage attached to a protractor. The slanting time-base shown on the B-scope display indicates the presence of any reflecting surfaces in the body of the scanned object by a persistent glow on the CRT screen. This device and its applications will be presented as a paper at ‘Ultrasonics for Industry’ in October. D.O. Sproule, Videoson, 121 Elgin Crescent, London Wll ULTRASONICS July 1969
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