Nanogen Inc, developer of molecular and point-of-care diagnostic products, announced that it was issued US Patent No. 6,753,148, "Methods and Apparatus for Detecting Variants Utilizing Base Stacking," by the US Patent and Trademark Office, a company release said.

The '148 patent is a continuation of patents issued to Nanogen that cover methods and apparatus that are particularly useful for detecting varying lengths of genetic variants. The patent covers the application of base stacking technologies that use specific types of oligonucleotides, both capture and probe oligonucleotides, to bind and discriminate nucleic acid sequences of differing lengths.

Actually, variations in nucleic acid sequences had to be detected by using electrophoresis, a tedious and multi-step process, to determine fragment sizes. With this new and novel approach, the nucleic acid sequence variants can be detected by hybridization and be included in DNA/RNA array panels. The issuance of patent '148 expands Nanogen's intellectual property portfolio to 59 patents issued within the United States, the release says.

The new patent describes methods and apparatus whereby capture and probe oligonucleotides are used to bind to a target nucleic acid sequence resulting in differing possible positions of the terminal nucleotides for both the capture and probe oligonucleotides. The positions of these terminal nucleotides are controlled by the length of the target sequence. When the terminal nucleotides are adjacent, the internal energy of base stacking increases, thereby increasing the stability of the complex as compared to complexes formed with lower stability, either because the sequences are mismatched or the terminal nucleotides of the capture and probe oligonucleotides are not adjacent.

"The use of technologies in this patent address the need for a novel approach to discriminate between differences in length of genetic variants, a requirement for broad application of microarrays," said Howard C Birndorf, Nanogen chairman and chief executive officer.