35. The specific activity of an enzyme in a crude extract of E. coli is 9.5 units/mg of protein. The specific activity increased to 68 units/mg of protein upon ion-exchange chromatography. The fold purification is __________.
Fold purification measures how much purer the enzyme sample is after a purification step, calculated as the ratio of specific activities. Here, specific activity rises from 9.5 units/mg in the crude E. coli extract to 68 units/mg after ion-exchange chromatography, yielding a fold purification of 7.2. This value indicates effective removal of contaminating proteins while retaining enzyme activity.
Calculation Details
Divide the final specific activity by the initial one: 68 ÷ 9.5 = 7.15789, rounded to 7.2 for typical biochemical reporting precision.
Specific activity (units/mg protein) reflects enzyme molecules active per protein mass, increasing as impurities decrease. No volume or total activity data is needed, as fold purification uses only specific activities.
Option Analysis
Though options are not listed, common choices from similar problems include 2.2, 3.5, 6.5, and 7.1.
- 2.2 or 3.5: Too low; these might arise from misdividing (e.g., 9.5 into 20-33).
- 6.5: Close but underestimates (e.g., from 62 units/mg).
- 7.1: Approximates but ignores full precision (
68/9.5 ≈ 7.16); 7.2 is exact.
Understanding Fold Purification
The fold purification enzyme E coli crude extract ion-exchange chromatography process is a cornerstone of biotechnology, quantifying enzyme purity gains from 9.5 units/mg protein in crude extracts to 68 units/mg post-purification. This metric guides researchers in molecular biology and biochemical engineering toward optimized protocols.
Fold purification equals final specific activity divided by crude specific activity. For this case, 68/9.5 = 7.2, showing a 7.2-fold increase via ion-exchange, which separates proteins by charge. Track this across steps to assess yield and purity in E. coli enzyme workflows.
Step-by-Step Calculation Guide
- Measure crude specific activity: 9.5 units/mg.
- Post-ion-exchange: 68 units/mg.
- Compute ratio: Precise division yields
7.15789, reported as 7.2. - Interpret: Higher folds mean fewer impurities, vital for downstream applications like fermentation.
Applications in Biotech
Ion-exchange chromatography boosts specific activity by eluting target enzymes selectively. In E. coli systems, this achieves 7-fold purity gains, aiding genomics and microbial biotech research. Combine with assays for total yield monitoring.
