Bioactive brassinosteroid levels are also modulated by a variety of inactivation or catabolic reactions, including epimerization, oxidation, hydroxylation, sulfonation, and conjugation to glucose or lipids.

TLS Online TPP Program

#Id: 4717

#Unit 13. Methods in Biology

n. Carotenoids, for instance, are a large class of red, yellow and orange plant pigments composed of long carbon chains with many conjugated double bonds. They contain three maxima in the visible region of the electromagnetic spectrum (420 nm, 450 nm, 480 nm).

TLS Online TPP Program

#Id: 4718

#Unit 13. Methods in Biology

Electron delocalisation extends throughout the cyclic tetrapyrrole ring of porphyrins and gives rise to an intense transition at 400 nm called the Soret band.

TLS Online TPP Program

#Id: 4719

#Unit 13. Methods in Biology

Molecules such as FAD (flavin adenine dinucleotide), NADH and NADþ are important coenzymes of proteins involved in electron transfer reactions (RedOx reactions). They can be conveniently assayed by using their UV/Vis absorption: 438 nm (FAD), 340 nm (NADH) and 260 nm (NADþ).

TLS Online TPP Program

#Id: 4720

#Unit 13. Methods in Biology

The absorption of UV light by nucleic acids arises from n!p* and p!p* transitions of the purine (adenine, guanine) and pyrimidine (cytosine, thymine, uracil) bases that occur between 260 nm and 275 nm. 

TLS Online TPP Program

#Id: 4721

#Unit 13. Methods in Biology

The absorption spectra of the bases in polymers are sensitive to pH and greatly influenced by electronic interactions between bases.

TLS Online TPP Program

#Id: 4722

#Unit 13. Methods in Biology

Biochemical samples are usually buffered aqueous solutions, which has two major advantages. Firstly, proteins and peptides are comfortable in water as a solvent, which is also the ‘native’ solvent. Secondly, in the wavelength interval of UV/Vis (700–200 nm) the water spectrum does not show any absorption bands and thus acts as a silent component of the sample