Biomaterial Database

Effects of ultrasound on nucleic acid bases. 1977

J R McKee, and C L Christman, and W D O'Brien, and S Y Wang

To understand the effects of ultrasound in biological systems at the molecular level, sonolysis of nucleic acid bases at sonic intensities less than or equal to 5 W/cm2 was studied. These sonoreactions were followed by UV-spectral decrease and by sonoproduct analysis. The order of reactivity was found to be thymine greater than uracil greater than cytosine greater than guanine greater than adenine. The extent of sonoreactions depends on the exposure time and the rate of the intensity. Aeration was necessary for maintenance of a reasonable reaction rate. "Threshold" intensities for uracil and thymine were observed at approximately 0.5 W/cm2. The effectiveness of the dissolved gases in producing sonoreactions was Ar greater than 02 greater than air greater than N2 greater than He greater than N2O, suggestive of free radicals mediating these reactions since N2O is an effective radical scavenger. Studies of the effects of substituents have shown that electronic rather than steric effects may have a greater influence. Preliminary identification indicates that cis- and trans-uracil glycols are the major products of uracil. Thus, a stepwise mechanism of pyrimidine sonolysis is proposed. Sonolysis of a dilute aqueous solution of uracil yielded pseudo-first-order kinetics in terms of [Ura] with a rate constant of 3.9 X 10(-2) min-1, implying that the rate-limiting step is the reaction of HO- with the base.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D003596	Cytosine	A pyrimidine base that is a fundamental unit of nucleic acids.
D005740	Gases	The vapor state of matter; nonelastic fluids in which the molecules are in free movement and their mean positions far apart. Gases tend to expand indefinitely, to diffuse and mix readily with other gases, to have definite relations of volume, temperature, and pressure, and to condense or liquefy at low temperatures or under sufficient pressure. (Grant & Hackh's Chemical Dictionary, 5th ed)
D006147	Guanine
D000225	Adenine	A purine base and a fundamental unit of ADENINE NUCLEOTIDES.	Vitamin B 4,4, Vitamin B,B 4, Vitamin
D013329	Structure-Activity Relationship	The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.	Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships
D013941	Thymine	One of four constituent bases of DNA.	5-Methyluracil,5 Methyluracil
D013997	Time Factors	Elements of limited time intervals, contributing to particular results or situations.	Time Series,Factor, Time,Time Factor
D014465	Ultrasonics	A subfield of acoustics dealing in the radio frequency range higher than acoustic SOUND waves (approximately above 20 kilohertz). Ultrasonic radiation is used therapeutically (DIATHERMY and ULTRASONIC THERAPY) to generate HEAT and to selectively destroy tissues. It is also used in diagnostics, for example, ULTRASONOGRAPHY; ECHOENCEPHALOGRAPHY; and ECHOCARDIOGRAPHY, to visually display echoes received from irradiated tissues.	Ultrasonic
D014498	Uracil	One of four nucleotide bases in the nucleic acid RNA.