3-1.3.3 Silver Staining:

Silver staining based on reduction of silver nitrate is more sensitive than ethidium bromide for double stranded DNA, as well as detection of single stranded DNA or RNA with a good sensitivity (in picogram level). It is based on the reduction of silver cations to insoluble silver metal by nucleic acids. This chemical reaction is insensitive to the macrostructure of the DNA molecule. Reduced silver molecules deposit in the gel around the DNA bands, creating a dark black band like image (i.e. “latent image”). Then the latent image can be developed to visualize by soaking the gel in a solution of silver cations (Silver nitrate) and a reducing agent (eg. formaldehyde). The silver granules in the latent image catalyze the further reduction and deposition of silver from the solution. Bands manifest as dark brown or black regions which appear before significant background develops. Development is stopped by altering the pH of the gel to a point where silver reduction is no longer favored.

3-1.3.4 Nanodrop:

Detection assays are persistently being developed that use progressively smaller amounts of nucleic acid, often precluding the use of conventional cuvette-based instruments for nucleic acid quantitation for those that can perform micro-volume quantitation. The patented NanoDrop microvolume sample retention system functions by combining fiber optic technology and natural surface tension properties to capture and retain small amounts of sample . This is a novel technology which allows us to measure nano-liter volumes (pico concentration) of the nucleic acid (DNA or RNA) sample. It is a type of spectrophotometer with a smaller sample size (as much less as 1-2 microlitre) requirement and higher sensitivity (even upto pico molar level). This is also a time saving technology widely used in basic molecular biology research.

Fig. 3-1.3.4 NanoDrop^® ND-1000 Spectrophotometer
(Source: http://www.biotech.wisc.edu/facilities/gec/equipment/nanodropnd1000)