Failure Case Library

Real lab failures, root causes, and fixes — curated and bilingually annotated by our team.

All Techniques (7) PCR (Sigma Guide) (12) End-point PCR Primers (9) Western Blot (9) Wound Healing Assay (5) Cell Culture (Contamination) (7) Lipid Transfection (8) CCK-8 Cell Viability Assay (5) Colony Formation Assay (10) Transfection (8) Nucleic Acid Quantification (9) Transfection (Co-transfection) (1) Protein Extraction (4) Plasmid Construction (Double Digest) (1) Sanger Sequencing (2) Plasmid Construction (1) qPCR (RT-qPCR) (5) Transwell Migration / Invasion Assay (5) Immunohistochemistry (IHC) (6) PCR (Polymerase Chain Reaction) (26) Restriction Enzyme Digest (13) DNA Cleanup & Plasmid Purification (7) RNA Cleanup (4) NGS Library Preparation (NEBNext Ultra II) (7) HMW DNA Extraction (Monarch) (7) LAMP (Loop-mediated Isothermal Amplification) (7) RNA Depletion for RNA-seq (7) Bacterial rRNA Depletion (4) Cell-free DNA Extraction (8) ELISA (Competitive) (18) ELISA (Signal Problems) (11) ELISA (High Background) (8) ELISA (Inconsistent Results / High CV) (6) ELISA (Standard Curve Fit Problems) (6) Western Blot (Weak / No Signal) (6) Western Blot (Detection Problems) (7) Western Blot (Bands at Wrong MW) (5) Western Blot (Misshapen / Uneven Bands) (5) Western Blot (Unexpected Multiple Bands) (7) Western Blot (Unusual Gel Band Appearance) (3) ChIP (High Background) (1) ChIP (Low Resolution with High Background) (6) ChIP (Low Signal) (8) ChIP (PCR Amplification Problems) (4) Immunohistochemistry (High Background) (9) Immunohistochemistry (No Staining) (9) Immunoprecipitation (High Antibody Elution) (1) Immunoprecipitation (High Background) (8) Immunoprecipitation (No Protein Detected) (5) Immunoprecipitation (Protein Obstruction) (1) ELISPOT (8) Tissue Imaging (Autofluorescence) (9) Flow Cytometry (Troubleshooting) (8) ELISA Development (9) Flow Cytometry (Autofluorescence) (7) Flow Cytometry (Compensation) (7) Flow Cytometry (Fc Blocking) (7) Flow Cytometry (Fixation & Permeabilization) (9) Flow Cytometry (Isotype Controls) (7) Flow Cytometry (Fixation Buffers) (7) Western Blot (CST Guide) (8) ChIP (CST Guide) (8) Immunoprecipitation (CST Guide) (14) Immunohistochemistry (CST Guide) (14) Flow Cytometry (CST Guide) (8) ELISA (R&D Guide) (10) ELISA (Sigma Guide) (6) Western Blot Immunodetection (19) IP-Western Blot (6) Flow Cytometry (Sample Considerations) (14) Flow Cytometry (Paraformaldehyde Fixation) (14) Western Blot (Sigma Protocol) (8) PCR / RT-PCR Amplification Problems (5) Cell Culture (Cell Death) (8) Cell Culture (Precipitates) (6) PCR (Invitrogen Guide) (8) PCR / qPCR Plastics (9) Flow Cytometry (Controls) (8) Plasmid Mini-prep (1) Transfection (siRNA Knockdown) (1) Western Blot (Blue Background) (1)
Flow Cytometry (Isotype Controls) severe

Isotype Control Signal Is Abnormally High

The isotype control antibody shows unexpectedly high fluorescence signal, making it difficult to distinguish true positive staining from background in flow cytometry analysis.

💡 6 causes ✓ 6 fixes
Flow Cytometry (Isotype Controls) severe

Isotype Control Signal Matches Test Antibody Signal

The fluorescence intensity from the isotype control is comparable to or overlaps with the test antibody signal, suggesting either no specific binding or incorrect experimental setup.

💡 5 causes ✓ 5 fixes
Flow Cytometry (Isotype Controls) moderate

Common Pitfalls in Isotype Control Selection

Experimental results show inconsistent or unreliable background measurements due to mismatched isotype control parameters that do not properly reflect non-specific binding.

💡 4 causes ✓ 4 fixes
Flow Cytometry (Isotype Controls) moderate

High Non-Specific Binding After Cell Fixation

Following fixation with formaldehyde or paraformaldehyde, both test antibodies and isotype controls show elevated background signal and increased non-specific staining patterns.

💡 4 causes ✓ 5 fixes
Flow Cytometry (Isotype Controls) severe

Excessive Background in Myeloid-Rich Cell Populations

Samples enriched for monocytes, macrophages, or dendritic cells show uniformly high fluorescence across all antibody channels including isotype controls, obscuring specific marker detection.

💡 4 causes ✓ 5 fixes
Flow Cytometry (Isotype Controls) moderate

Poor Signal-to-Noise Ratio with Dim Fluorophores on Weak Markers

Weak or low-abundance markers show poor separation from negative populations and isotype controls, especially when conjugated to dim fluorophores, making population discrimination difficult.

💡 4 causes ✓ 6 fixes
Flow Cytometry (Isotype Controls) severe

Incorrect Use of Isotype Controls for Gating Dim Markers

Gates set using isotype controls for dim or activation markers result in inaccurate population identification, with either false negatives (missed positive cells) or false positives.

💡 4 causes ✓ 5 fixes