SDS-PAGE Gel- Figure Legend Examples
What Figure Legends Actually Are
Figure legends are the captions below your images. They tell readers exactly what they're looking at and how to interpret it. Bad legends confuse reviewers. Good legends make your data impossible to misinterpret.
For SDS-PAGE gels specifically, legends need to communicate the experimental setup, molecular weights, and what the bands represent. Nothing more, nothing less.
The Anatomy of a Solid SDS-PAGE Gel Legend
Every figure legend needs these elements:
- Migration conditions — percentage gel, voltage, run time
- Sample identification — what each lane contains
- Molecular weight markers — which ladder you used and key band sizes
- Loading amount — μg of protein per lane
- Relevant annotations — arrows, brackets, or asterisks explained in the text
What to Include (and What to Leave Out)
Don't pad your legend with methods. Buffer compositions, incubation times, and antibody details belong in Materials and Methods. The figure legend is for quick reference—it answers "what am I seeing?" not "how did you do this?"
SDS-PAGE Figure Legend Examples That Actually Work
Example 1: Basic Coomassie Stain
Bad legend:
"Figure 1. SDS-PAGE analysis of protein samples. The gel shows various protein bands."
This tells readers nothing. "Various protein bands" is useless.
Good legend:
"Figure 1. Coomassie-stained 12% SDS-PAGE of whole cell lysates. Lanes: M, PageRuler Plus (10–250 kDa); 1, untreated HEK293 cells; 2, HEK293 cells transfected with pCMV-Myc; 3, HEK293 cells transfected with pCMV-Myc-ΔCT. Twenty micrograms of total protein loaded per lane. Arrow indicates expected size of Myc-ΔCT (42 kDa)."
This works because any reader can replicate the gel conditions and identify the band of interest.
Example 2: Western Blot
Bad legend:
"Figure 2. Western blot showing protein expression levels."
No. Just no.
Good legend:
"Figure 2. Immunoblot analysis of p53 and GAPDH in HCT116 cells. Whole cell lysates (30 μg) were resolved on 10% SDS-PAGE and probed with anti-p53 (1:1000) and anti-GAPDH (1:5000). Lane assignments: 1, untreated; 2, 24 h post-irradiation; 3, 48 h post-irradiation. GAPDH served as loading control. Molecular weights indicated at right."
Example 3: Multiple Gels in One Figure
Bad legend:
"Figure 3. Analysis of samples by SDS-PAGE and western blot."
Good legend:
"Figure 3. Purification of His-SUMO-hTERT from E. coli. (A) Coomassie-stained 12% SDS-PAGE of IMAC fractions. Lane 1, flow-through; 2, wash (20 mM imidazole); 3, elution (250 mM imidazole). (B) Corresponding anti-His western blot. Arrowhead indicates His-SUMO-hTERT (89 kDa). M, BenchMark (10–200 kDa)."
Common Mistakes That Kill Your Legends
- Missing molecular weight markers. Always indicate which ladder and label key bands. Reviewers will ask.
- Unlabeled lanes. If you have 12 lanes, all 12 need identification.
- Vague descriptions. "Protein bands" is not a description. Name the specific protein or state the experimental question.
- Overloading with methods. Don't list buffer recipes in the figure legend.
- Forgetting loading amounts. This is critical for reproducibility.
- No annotation explanations. If you put asterisks or arrows in the figure, explain them in the legend.
Quick Reference: Legend Components by Gel Type
| Gel Type | Required Information |
|---|---|
| Coomassie/Silver stain | Gel %, sample ID, MW marker, loading amount, any annotations explained |
| Western blot | Everything above PLUS primary/secondary antibodies, dilutions, detection method |
| 2D gel | Isoelectric point range, molecular weight axis, sample preparation, stain used |
| Native gel | Buffer conditions, stain, whether native or semi-native, activity assay if applicable |
How to Write Better Legends: A Practical Workflow
Step 1: Start With the Gel Conditions
Open with the basics. "12% SDS-PAGE" or "4–20% gradient gel" comes first. This orients the reader immediately.
Step 2: List Your Samples
Use "Lanes: 1, untreated; 2, treated with 100 μM drug; 3, treated with 100 μM drug + inhibitor" format. Keep it tight.
Step 3: Add the MW Marker
"M, PageRuler Prestained (10–180 kDa)" or similar. If you're showing a specific band size, label it on the figure and mention it in the legend.
Step 4: Include Loading Control Info
For westerns, note the housekeeping gene or total protein stain used. For Coomassie, state total protein loaded.
Step 5: Explain Annotations
One sentence: "Arrow indicates GFP-VPS26 (~28 kDa). Asterisk marks nonspecific band." That's it.
Real Examples From Published Papers
Most journals follow a standard format. Here are templates you can adapt:
Template 1 (Coomassie):
"[Stain]-stained [percentage]% SDS-PAGE of [sample description]. Lanes: M, [marker name and size range]; 1–[n], [sample descriptions]. [Number] μg of total protein loaded per lane. [Annotation explanation if applicable]."
Template 2 (Western):
"Immunoblot of [protein(s)] in [cell/tissue type]. [Percentage]% SDS-PAGE with [number] μg [sample type] per lane. Blots probed with [antibody] at 1:[dilution]. Lane assignments: [list]. [Loading control] used as loading control. [Annotation explanation]."
Template 3 (Multiple panels):
"(A) [Description of panel A]. (B) [Description of panel B]. (C) [Description of panel C]. M, [marker]. [Annotation explanations]."
The Bottom Line
Figure legends exist to make your data readable without supplementary materials. A reviewer should understand your gel completely by reading the legend alone.
If you're writing "various bands" or "protein expression," you're doing it wrong. Name the proteins. State the conditions. Label the lanes. That's the entire job.