Question

What is expected to happen to absorbance at 340 nm if functional DHFR is present in a reaction mix containing DHF, NADPH, and DHFR?

Answer 1

The absorbance at 340 nm is expected to decrease if functional DHFR is present in a reaction mix containing DHF, NADPH, and DHFR.

Step-by-step explanation:

In a reaction mix containing DHF (dihydrofolate), NADPH (nicotinamide adenine dinucleotide phosphate), and DHFR (dihydrofolate reductase), the absorbance at 340 nm is indicative of the reduction of DHF to tetrahydrofolate (THF) catalyzed by DHFR. The decrease in absorbance at 340 nm corresponds to the consumption of NADPH during this reduction reaction.

The reaction can be represented as follows:

`\[ \text{DHF} + \text{NADPH} + \text{H}^+ \xrightarrow{\text{DHFR}} \text{THF} + \text{NADP}^+ \]`

During this process, DHFR utilizes NADPH as a reducing agent to convert DHF to THF, leading to a decrease in the concentration of NADPH. The absorbance at 340 nm is directly proportional to the concentration of NADPH. Therefore, a reduction in NADPH concentration results in a decrease in absorbance at 340 nm.

This change in absorbance is a measure of the progress of the reaction, providing valuable information about the enzymatic activity of DHFR. The decrease in absorbance at 340 nm is a characteristic signal indicating the successful functioning of DHFR in the reaction mix, confirming its role in the reduction of DHF.