Regulable toehold lock for the effective control of strand displacement reaction sequence and circuit leakage

Strand displacement reaction enables the construction of enzyme-free DNA reaction networks,thus has been widely applied to DNA circuit and nanotechnology.It has the characteristics of high efficiency,universality and regulatability.However,the existing regulation tools cannot enable effective control of the reaction sequence,which undoubtedly limits the construction of complex nucleic acid circuits.Herein,we developed a regulation tool,toehold lock,and achieved strict control of reaction sequence without loss of the main reaction signal output.Furthermore,we applied the tool to scenarios such as seesaw circuits,AND/OR logic gates,and entropy-driven circuits,and respectively demonstrated its significant superiority compared to the original method.We believe that the proposed toehold lock has greatly optimized the efficiency of DNA strand displacement-based networks,and we anticipate that the tool will be widely used in multiple fields.

Mossbauer Spectrum Study on Hydrogen Reduction of Preoxidized Ilmenite

Reduction behavior of preoxidized synthetic ilmenite was studied by means of Mossbauer spectra. In the course of reduction, iron component in the samples is reduced in stepwise: Fe 3+ →Fe 2+ →Fe 0, and some intermediate compounds, such as Fe 3O 4, Fe 2TiO 4 etc . and their solid solution may be generated besides Fe 2O 3 and FeTiO 3. If the reduction temperature is higher than 1173 K, the metallization needs only half time of the case when the temperature is lower than 1073 K.

DETECTION OF HUMAN PAPILLOMAVIRUS TYPES 16, 18 DNA RELATED SEQUENCES IN BRONCHOGENIC CARCINOMA BY POLYMERASE CHAIN REACTION

In studying the relationship between human papillomavirus (HPV) and bronchogenic carcinoma, 'high-risk' HPV 16, 18 DNA sequences were detected in samples from 50 lung cancer patients, 18 patients with benign pulmonary diseases and 4 fetal lung tissues by polymerase chain reaction (PCR) and dot-blot hybridization with biotin-labelled probes. The results showed that HPV 16, 18 DNA related sequences were found in 32% of lung cancer specimens, with 10 cases of HPV 16, 5 cases of HPV 18 and 1 case of both types. 48.15% (13 / 27) of squamous cell carcinomas were shown to be positive for HPV 16, 18 DNA. In addition, two adenocarcinomas and one small cell carcinoma were positive for HPV 16 DNA. No specimens from benign diseases tissues and fetal lung tissues showed positive results. These results suggest that primary bronchogenic carcinoma is related to HPV infection.

Amino acid identification and sequence analysis of peptides by reaction mass spectrometry

Fast atom bombardment mass spectrometry (FAB-MS) is applied to distinguish N- terminal series ions from C-terminal series ions of a peptide by on-probe acetylation, it provides valuable information about the sequence of an unknown peptide. The FAB mass spectra contain a number of characteristic ions at low-mass region in addition to the sequence ions at high-mass region. It was found that the ions below m/z 200 are characteristic of the amino acid composition of the peptide, from which the amino acid composition of the peptide could be estimated. Additionally, mixture analysis is also discussed.

Genotyping for Kidd, Kell, Duffy, Scianna, and RHCE blood group antigens polymorphisms in Jiangsu Chinese Han

Background Molecular testing is more precise compared to serology and has been widely used in genotyping blood group antigens. Single nucleotide polymorphisms （SNPs） of blood group antigens can be determined by the polymerase chain reaction with sequence specific priming （PCR-SSP） assay. Commercial high-throughput platforms can be expensive and are not approved in China. The genotype frequencies of Kidd, Kell, Duffy, Scianna, and RhCE blood group antigens in Jiangsu province were unknown. The aim of this study is sought to detect the genotype frequencies of Kidd, Kell, Duffy, Scianna, and RhCE antigens in Jiangsu Chinese Hart using molecular methods with laboratory developed tests. Methods DNA was extracted from EDTA-anticoagulated blood samples of 146 voluntary blood donors collected randomly within one month. Standard serologic assay for red blood cell antigens were also performed except the Scianna blood group antigens. PCR-SSP was designed to work under one PCR program to identify the following SNPs： JK1/JK2, KEL 1/KEL2, FYA/FYB, SC1/SC2, C/c and E/e. Results Serologic antigen results were identical to the phenotypes that were predicted from genotyping results. The allele frequencies for Jk^＊01 and Jk^＊02 were 0.51 and 0.49, respectively; for Fy^＊A and Fy^＊B 0.94 and 0.06; for RHCE^＊C and RHCE^＊c 0.68 and 0.32; and for RHCE^＊E and RHCE^＊e 0.28 and 0.72. Among 146 blood donors, all were KEL^＊02/ KEL^＊02 and SC^＊01/SC^＊01, indicating allele frequencies for KEL^＊02 and SC^＊01 close to 1.00. Conclusions The use of PCR-SSP working under the same condition for testing multiple antigens at the same time is practical. This approach can be effective and cost-efficient for small-scale laboratories and in developing counties. These molecular tests can be also used for identifying rare blood types.

Study on vertical transmision of Chlamydia trachomatis using PCR and DNA sequencing

Objective To investigate the vertical transmission rate of Chlamy dia trachomatis (CT) in Chongqing, China. Methods Specimens taken from 278 women and from their 79 infants were e xamined b y cell culture, polymerase chain reaction (PCR) and DNA sequence analysis. Chlam ydia trachomatis was isolated in McCoy cell culture. CT DNA was extracted with a modified NaI method. After cloning, recombinant plasmids were used for sequence analysis with the dideoxy chain termination method.Results 10.8% (30/278) of the cervical cultures of pregnant women were positive for Chlamydia trachomatis, while the positive rate tested by PCR was 14.0% (39/2 78). The vertical transmission rate of Chlamydia trachomatis was 55. 0% (11/20). The incidences of conjunctivitis and pneumonia in infants with Chlamydia t rachom atis positive mothers were 27.3% and 18.2%, respectively. DNA sequence s of Chlam ydia trachomatis isolated from the cervix of a mother and the nasopharynx of her baby were identical.Conclusion Chlamydia trachomatis infection is quite common in Cho ngqing , China. Our report is the first report of CT vertical transmission proved by DN A sequence analysis.