Let k ? 2, 1 ? i ? k and α ? 1 be three integers. For any multiset which consists of some k-long oligonucleotides, a DNA labelled graph is defined as follows: each oligonucleotide from the multiset becomes a point; t...Let k ? 2, 1 ? i ? k and α ? 1 be three integers. For any multiset which consists of some k-long oligonucleotides, a DNA labelled graph is defined as follows: each oligonucleotide from the multiset becomes a point; two points are connected by an arc from the first point to the second one if the i rightmost nucleotides of the first point overlap with the i leftmost nucleotides of the second one. We say that a directed graph D can be (k, i; α)-labelled if it is possible to assign a label (l 1(x), ..., l k (x)) to each point x of D such that l j (x) ? {0, ..., α ? 1} for any j ? {1, ..., k} and (x, y) ? E(D) if and only if (l k?i+1(x), ..., l k (x)) = (l 1(y), ..., l i (y)). By the biological background, a directed graph is a DNA labelled graph if there exist two integers k, i such that it is (k, i; 4)-labelled. In this paper, a detailed discussion of DNA labelled graphs is given. Firstly, we study the relationship between DNA labelled graphs and some existing directed graph classes. Secondly, it is shown that for any DNA labelled graph, there exists a positive integer i such that it is (2i, i; 4)-labelled. Furthermore, the smallest i is determined, and a polynomial-time algorithm is introduced to give a (2i, i; 4)-labelling for a given DNA labelled graph. Finally, a DNA algorithm is given to find all paths from one given point to another in a (2i, i; 4)-labelled directed graph.展开更多
Objective To explore if strand breaks of DNA in human early chorionic villus cells in uterus were induced by diagnostic ultrasound and to evaluate the method used for detection of single-stranded breaks and double-str...Objective To explore if strand breaks of DNA in human early chorionic villus cells in uterus were induced by diagnostic ultrasound and to evaluate the method used for detection of single-stranded breaks and double-stranded breaks in human DNA. Methods 60 normal pregnant women aged 20-30, who underwent artificial abortion during 6-8 weeks of gestation, were randomly divided into 2 experimental groups: All 30 cases were exposed to diagnostic ultrasound in uterus for 10 minutes, and 24 hours later chorionic villi were extracted; the other 30 cases were taken as the control group. Single-stranded DNA and double-stranded DNA in villus cells in all cases were isolated by the alkaline unwinding combined with hydroxylapatite chromatography, and were quantitatively detected using 32 P-labeled Alu probe for dot-blotting hybridization. Results There was no significant difference in quantity and percentage in single-stranded DNA and double-stranded DNA between 2 groups (P>0.05). 32 P-Alu probe could only hybridize with human DNA, and could detect DNA isolated from as few as 2.5×10 3 chorionic villus cells and 0.45ng DNA in human leukocytes. Conclusion The results suggested that there were no DNA strand damages in human chorionic villus cells when the uterus was exposed to diagnostic ultrasound for 10 minutes. The method,^(32)P-Alu probe for dot-blotting hybridization, was even more specific, sensitive and accurate than conventional approaches.展开更多
基金the National Natural Science Foundation of China (Grant No. 10471081)
文摘Let k ? 2, 1 ? i ? k and α ? 1 be three integers. For any multiset which consists of some k-long oligonucleotides, a DNA labelled graph is defined as follows: each oligonucleotide from the multiset becomes a point; two points are connected by an arc from the first point to the second one if the i rightmost nucleotides of the first point overlap with the i leftmost nucleotides of the second one. We say that a directed graph D can be (k, i; α)-labelled if it is possible to assign a label (l 1(x), ..., l k (x)) to each point x of D such that l j (x) ? {0, ..., α ? 1} for any j ? {1, ..., k} and (x, y) ? E(D) if and only if (l k?i+1(x), ..., l k (x)) = (l 1(y), ..., l i (y)). By the biological background, a directed graph is a DNA labelled graph if there exist two integers k, i such that it is (k, i; 4)-labelled. In this paper, a detailed discussion of DNA labelled graphs is given. Firstly, we study the relationship between DNA labelled graphs and some existing directed graph classes. Secondly, it is shown that for any DNA labelled graph, there exists a positive integer i such that it is (2i, i; 4)-labelled. Furthermore, the smallest i is determined, and a polynomial-time algorithm is introduced to give a (2i, i; 4)-labelling for a given DNA labelled graph. Finally, a DNA algorithm is given to find all paths from one given point to another in a (2i, i; 4)-labelled directed graph.
基金supported by the National Natural Science Foundation of China(Grant Nos.6053301030670540+4 种基金60874036and 60503002)the National High Technology Research and Development Program(863 Program)(Grant No.2006AA01Z104)the Ph.D. Programs Foundation of the Ministry of Education of China(Grant No.20070001020)the Postdoctoral Science Foundation of China(Grant No.20060400344)
文摘Objective To explore if strand breaks of DNA in human early chorionic villus cells in uterus were induced by diagnostic ultrasound and to evaluate the method used for detection of single-stranded breaks and double-stranded breaks in human DNA. Methods 60 normal pregnant women aged 20-30, who underwent artificial abortion during 6-8 weeks of gestation, were randomly divided into 2 experimental groups: All 30 cases were exposed to diagnostic ultrasound in uterus for 10 minutes, and 24 hours later chorionic villi were extracted; the other 30 cases were taken as the control group. Single-stranded DNA and double-stranded DNA in villus cells in all cases were isolated by the alkaline unwinding combined with hydroxylapatite chromatography, and were quantitatively detected using 32 P-labeled Alu probe for dot-blotting hybridization. Results There was no significant difference in quantity and percentage in single-stranded DNA and double-stranded DNA between 2 groups (P>0.05). 32 P-Alu probe could only hybridize with human DNA, and could detect DNA isolated from as few as 2.5×10 3 chorionic villus cells and 0.45ng DNA in human leukocytes. Conclusion The results suggested that there were no DNA strand damages in human chorionic villus cells when the uterus was exposed to diagnostic ultrasound for 10 minutes. The method,^(32)P-Alu probe for dot-blotting hybridization, was even more specific, sensitive and accurate than conventional approaches.
