SsDNA base sequence detection

Selectivity of the DNA-based biosensor It can be truely considered as an analj ical parameter regarding the analj e detected such as a specific ssDNA base sequence or protein interacting with nucleic acid aptamer. Generally, class selectivity to DNA as the recognition element itself can be considered (e.g., at damage to DNA). 

Various experimental conditions have been optimized for DNA sequencing on a glass chip. These conditions include separation matrix (denaturing 3-4% LPA), separation temperature (35—40°C), channel length (7.0 cm), channel depth (50 pm), injector parameters (100-pm or 250-p.m double-T injector, 60-s loading time). These optimal conditions facilitated the one-color detection of separation of 500 bases of M13mpl8 ssDNA in 9.2 min, and four-color detection of 500-base separation in 20 min [548]. 

Typical DNA probes take 15 to 25 base pair long that are able to detect their target sequences. Besides probe, calf thymus double(ds) or single-stranded DNA (ssDNA) molecules also immobilized onto the recognition element of a biosensor. 

Large differences between the interfacial properties of ds and ssDNAs observed earlier by capacitance measurements [10, 37] suggested that a.c. impedance measurements could be used to detect DNA hybridization on electrodes [433, 434] (Sect. 12.8.). A three-component ODN system on a gold electrode (involving avidin-biotin interactions) was used to detect specific DNA sequences by means of faradaic impedance spectroscopy [435]. Impedance spectroscopy does not seem, however, to be the most convenient method for the DNA biosensor faster and simpler voltam-metric or chronopotentiometric methods will probably be more convenient. Gon-ductivity of the perfect DNA, contrasting with a loss of conductivity in duplexes with mismatched bases, may be of use in... 

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