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The secondary benefit of using spectrophotometric analysis for nucleic acid quantitation is the ability to determine sample purity using the 260 nm:280 nm calculation. The ratio of the absorbance at 260 and 280 nm (A 260/280 ) is used to assess the purity of nucleic acids.
In biochemistry, the molar absorption coefficient of a protein at 280 nm depends almost exclusively on the number of aromatic residues, particularly tryptophan, and can be predicted from the sequence of amino acids. [6] Similarly, the molar absorption coefficient of nucleic acids at 260 nm can be predicted given the nucleotide sequence.
The concentration of pure osmium tetroxide (molar mass = 254.23 g/mol) is c(OsO 4) = 5.1 kg/L / 254.23 g/mol = 20.1 mol/L. A typical protein in bacteria, such as E. coli, may have about 60 copies, and the volume of a bacterium is about 10 −15 L. Thus, the number concentration C is C = 60 / (10 −15 L) = 6 × 10 16 L −1. The molar ...
In particular, the pH of a solution can be predicted when the analytical concentration and pK a values of all acids and bases are known; conversely, it is possible to calculate the equilibrium concentration of the acids and bases in solution when the pH is known. These calculations find application in many different areas of chemistry, biology ...
[10]: 280–4 Hence, a single experiment can be used to measure the logarithms of the partition coefficient (log P) giving the distribution of molecules that are primarily neutral in charge, as well as the distribution coefficient (log D) of all forms of the molecule over a pH range, e.g., between 2 and 12.
The Henderson–Hasselbalch equation can be used to model these equilibria. It is important to maintain this pH of 7.4 to ensure enzymes are able to work optimally. [10] Life threatening Acidosis (a low blood pH resulting in nausea, headaches, and even coma, and convulsions) is due to a lack of functioning of enzymes at a low pH. [10]
Osmotic concentration, formerly known as osmolarity, [1] is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per litre (L) of solution (osmol/L or Osm/L). The osmolarity of a solution is usually expressed as Osm/L (pronounced "osmolar"), in the same way that the molarity of a solution is expressed as "M ...
Coupled assay for hexokinase using glucose-6-phosphate dehydrogenase. Even when the enzyme reaction does not result in a change in the absorbance of light, it can still be possible to use a spectrophotometric assay for the enzyme by using a coupled assay. Here, the product of one reaction is used as the substrate of another, easily detectable ...