Nylon Membranes for Molecular Detection
Membranes have been standard tools in life sciences laboratories since the 1970’s, when it was discovered that biomolecules could be spotted directly onto membranes or transferred from gels. The first membranes used for molecular detection were made from nitrocellulose, which has a high affinity for biomolecules and low background with many detection techniques. Difficulties with handling and exposure to heat led to a search for alternative solid supports.
For nucleic acids, nylon membranes were found to have higher binding, the structural integrity to withstand fixation temperatures, and the multiple steps involved with detection and reprobing.
Nucleic Acid Detection
Detection techniques are important for interpreting results in all areas of genomics research and molecular diagnostic applications. As sample sizes become more minute and less abundant, such as in forensic analysis, the need for highly sensitive detection platforms that exhibit extremely low background intensifies. At Pall, we understand your need for increased sensitivity and have the experience of more than 30 years of manufacturing membranes for nucleic acid detection to ensure consistent performance from lot-to-lot and blot-to-blot. Pall pioneered the first nylon membrane for nucleic acid transfer techniques and now our membranes set the standard for nucleic acid detection applications in leading laboratories around the world.
Our nylon membranes are cast from a nylon 6,6 polymer, which is mostly non-polar with terminal amino and carboxyl groups. When formed into a membrane, the molecule can exhibit a structure like the one shown below. (Fig. 3) The hydrophobic regions fold away from the surface of the pores so that the terminal polar groups are exposed. In this manner, a hydrophilic membrane can be formed from hydrophobic molecules.
Nylon 6,6 membranes provide excellent resolution, high sensitivity and low background for nucleic acid detection. Our nylon membranes are inherently hydrophilic and do not require prewetting, thereby facilitating ease of use. These membranes are considered the “gold standard” for critical molecular biology applications such as forensic detection, and are recommended for all nucleic acid detection procedures as well as protein dot ELISAs. Typical nucleic acid detection procedures require multiplecycles of hybridization, stripping, and reprobing dictating the need for a highly durable membrane. Our membranes exhibit high tensile strength and do not shrink, crack, or tear when subjected to such conditions. We have four different chemistries available to address a variety of applications. The selection chart at the end of this section will aid in selecting the optimal membrane for your application.
When selecting a membrane for nucleic acid procedures, it is important to consider the relative levels of sensitivity needed, the detection system employed and whether or not multiple probing’s will be required. The membranes listed below are all suitable for nucleic acid transfer and detection applications.
Biodyne®A, a amphotericnylon membrane is an uncharged Nylon 6,6 membrane. It has a high binding capacity for biomolecules and offers high sensitivity and nucleic acid retention. It is especially well suited for use with chemiluminescence, alkaline phosphatase or other detection systems where background is problematic.
Biodyne B, a positively-charged nylon membrane has pore surfaces populated by a high density of quaternary ammonium groups, making it strongly cationic. This positive charge is maintained over a broad pH range and promotes strong ionic binding of nucleic acids, making it ideal for transfer and detection of nucleic acids. Thispositively-charged nylon membrane will produce the highest possible sensitivity with radioactive probes.
Biodyne Plus, a positively-charged nylon with high isoelectric point membrane, like the positively-charged nylon membrane, this membrane contains pore surfaces populated by a high density of quaternary ammonium groups. This membrane has an extremely high isoelectric point which provides greater sensitivity than amphoteric nylon while exhibiting lower background than the standard positively charged nylon. It is our most sensitive nylon membrane for nucleic acid detection and is recommended for detection systems that produce high background produce high background.
Biodyne C, a negatively-charged nylon membrane that has pore surfaces populated by a high density of carboxyl groups. The membrane can be derivatized by coupling reactions with these groups. It is ideal for reverse dot blots and affinity purification.