Promoter mutations are also cis-acting. If they prevent RNA polymerase from binding at P-lac, the structural genes are never transcribed.

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#Unit 13. Methods in Biology

A photoelastic modulator (PEM) is then used to convert the linearly polarized light into circularly polarized light.

TLS Online TPP Program

#Id: 8070

#Unit 13. Methods in Biology

An optically active chiral compound will absorb the two directions of circularly polarized light by different amounts

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#Id: 8073

#Unit 13. Methods in Biology

In a chiral medium the molar absorptivity of LCP and RCP light are different so they will be absorbed by the medium in different amounts. 

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#Id: 8074

#Unit 13. Methods in Biology

Differential absorption of the two circularly polarized lights resulted in elliptically polarized light and CD is represented in terms of molar ellipticity(θ).

θ = 3298    ϵ

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#Id: 8075

#Unit 13. Methods in Biology

β-sheets shows a negative bands at 218nm and a positive one at 196nm.

Random coils has a positive band at 212nm and a negative one around 195nm.

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#Id: 8076

#Unit 13. Methods in Biology

CD can be used to estimate the structure of unknown proteins and monitor conformational changes due to temperature, mutations, heat, denaturants or binding interactions