LimsPulse
Bioanalytical

Gel electrophoresis system

A tank with buffer and electrodes, a gel and a DC power supply. Charged molecules such as proteins or DNA move through the gel in the electric field and separate by size, then are stained and imaged.

  • Biotechnology
  • Biopharmaceutical
  • Academic research
  • Diagnostics development
  • Food (protein profiling)
  • Vaccines
Photo of a Gel electrophoresis system
Photo: Lilly_M, CC BY-SA 3.0 (cropped), via Wikimedia Commons
LEARN & PRACTICE

Test your Gel electrophoresis knowledge

Multiple-choice questions

Pick an answer to see whether you are right and why.

  1. Q1. Why is SDS used in SDS-PAGE?

    basic

  2. Q2. Towards which electrode does DNA move in an agarose gel?

    basic

  3. Q3. Bands curve upwards at the edges ('smiling'). What is the most likely cause?

    intermediate

  4. Q4. In a power supply check, a 1000 Ω load is used at 100 V. What current is expected?

    intermediate

  5. Q5. What is the main safety rule before touching the buffer or removing the tank lid?

    basic

  6. Q6. Which gel would best separate small proteins of about 10–20 kDa?

    intermediate

  7. Q7. Under non-reducing SDS-PAGE an IgG runs near 150 kDa; under reducing conditions it gives bands near 50 and 25 kDa. Why?

    advanced

Viva questions

Think of your answer first, then open it to compare.

  1. 1. Why do we calibrate the electrophoresis power supply, and how?

    Field strength controls migration and heating, so the output must match the display. Using a calibrated multimeter and a known resistive load, compare displayed and measured voltage and current at several set points, check the timer, and confirm safety cut-outs work.

  2. 2. How would you estimate the molecular weight of an unknown protein band?

    Run a molecular weight marker on the same gel. Measure the migration distance of each marker band, plot log(MW) against relative mobility, fit a line over the linear region, and read the unknown's MW from its mobility.

  3. 3. Why have many biologics labs replaced SDS-PAGE with CE-SDS for purity testing?

    CE-SDS gives quantitative peaks with better precision, automation and data integrity, and avoids staining variation. SDS-PAGE remains useful for visual identity and quick checks, but its densitometry is only semi-quantitative.

In LimsPulse · Calibration Management

Keep every Gel electrophoresis in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how