SF1 (Ab-82) Antibody

Basic Research Questions

• What is SF1 protein and what are the key differences between Splicing Factor 1 and Steroidogenic Factor 1?

  SF1 can refer to two distinct proteins that researchers should not confuse:

  Splicing Factor 1 (SF1): A nuclear protein involved in RNA splicing and spliceosome assembly. In humans, the canonical protein has 639 amino acid residues and a molecular weight of approximately 68 kDa . It is widely expressed in multiple tissues including lung, ovary, adrenal gland, colon, kidney, and brain . The SF1 (Ab-82) antibody targets this protein specifically at the phosphorylation site of serine 82 .

  Steroidogenic Factor 1 (SF-1): A transcription factor encoded by the NR5A1 gene involved in sex determination and regulating genes related to reproductive glands and adrenal glands . It binds to the Ad4 site in the promoter region of steroidogenic P450 genes and regulates several other genes including AMH, AHCH, and STAR .

  Feature	Splicing Factor 1	Steroidogenic Factor 1
  Function	RNA splicing, spliceosome assembly	Transcriptional regulation of steroidogenic genes
  Gene Symbol	SF1	NR5A1
  Gene ID (NCBI)	7536	Various
  Subcellular Localization	Nuclear	Nuclear
  Key Domains	RNA-binding	DNA-binding
  Disease Associations	Various cancers	Adrenal failure, gonadal dysgenesis, male infertility

• What epitope does the SF1 (Ab-82) Antibody recognize and how does this impact its applications?

  The SF1 (Ab-82) Antibody specifically recognizes a non-phosphopeptide derived from human Splicing Factor 1 around the phosphorylation site of serine 82 (S-P-SP-P-E) . This specificity is important because:

  • It enables detection of total SF1 protein regardless of phosphorylation status

  • It can be used in comparative studies with phospho-specific antibodies to assess SF1 activation

  • The epitope is conserved across human, mouse, and monkey samples

  The antibody was produced by affinity-purification from rabbit antiserum using epitope-specific immunogen . This targeted approach enhances specificity but researchers should note that the epitope might be masked in certain experimental conditions or protein conformations.

• What applications has SF1 (Ab-82) Antibody been validated for and what are the recommended dilutions?

  Based on validation studies, the SF1 (Ab-82) Antibody has been confirmed effective for multiple applications:

  Application	Recommended Dilution	Notes
  Western Blot (WB)	1:500-1:1000	Detects band at 65-71 kDa
  Immunohistochemistry (IHC)	1:50-1:100	Works on paraffin-embedded tissues; validated on human brain tissue
  Immunofluorescence (IF)	1:100-1:500	Validated on HeLa cells
  ELISA	1:20000	High sensitivity for this application

  For optimal results in Western blotting, some sources recommend a broader dilution range of 1:500-1:3000 , suggesting that researchers may need to empirically determine the optimal concentration for their specific samples.

Advanced Research Questions

• How does the phosphorylation state of SF1 affect antibody selection and experimental design?

  When investigating SF1 (Splicing Factor 1) function, distinguishing between total and phosphorylated protein is critical:

  • Total SF1 detection: The SF1 (Ab-82) Antibody recognizes total SF1 protein regardless of phosphorylation status at Ser82

  • Phospho-specific detection: Separate antibodies like Anti-Phospho-Splicing factor 1 (S82) specifically detect the phosphorylated form

  This distinction is crucial because:

  1. SF1 phosphorylation modulates its interaction with other splicing factors

  2. The phosphorylation state correlates with specific cellular processes and stress responses

  3. In signaling pathway studies, researchers need to track changes in phosphorylation rather than total protein levels

  For experimental design, researchers should consider:

  • Using both antibodies in parallel to calculate phosphorylation-to-total protein ratios

  • Including phosphatase treatments as controls to validate phospho-specific antibody specificity

  • Selecting appropriate positive controls (e.g., HeLa cells for WB experiments)

• What are the key considerations for using SF1 (Ab-82) Antibody in multiplexed immunoassays?

  When incorporating SF1 (Ab-82) Antibody into multiplexed assays, researchers must address several technical challenges:

  Species compatibility: The antibody is produced in rabbit, so avoid using other rabbit-derived antibodies in the same multiplex panel to prevent secondary antibody cross-reactivity .

  Fluorophore selection: For immunofluorescence applications, choose fluorophores that:

  • Have minimal spectral overlap

  • Are compatible with your microscopy setup

  • Consider the subcellular localization (nuclear for SF1) when selecting colors

  Antigen retrieval considerations: For IHC multiplexing, note that the recommended antigen retrieval method for SF1 detection involves:

  • TE buffer at pH 9.0 (preferred)

  • Alternative: citrate buffer at pH 6.0

  Sequential staining protocol: For complex multiplexing:

  1. Start with the weakest antibody (often not SF1)

  2. Apply SF1 (Ab-82) at optimal dilution (1:50-1:100 for IHC)

  3. Use fluorophore-conjugated or enzyme-labeled secondary antibodies

  4. Include appropriate blocking steps between antibody applications

• How does SF1 (Ab-82) Antibody performance compare in detecting endogenous versus overexpressed SF1 protein?

  The performance characteristics of SF1 (Ab-82) Antibody differ significantly between endogenous and overexpressed systems:

  Endogenous SF1 detection:

  • Sensitivity: The antibody reliably detects endogenous SF1 in HeLa and HepG2 cells by Western blot

  • Signal intensity: Moderate signal strength requires optimized exposure times

  • Background: Generally low background with proper blocking conditions

  • Tissue specificity: Detectable in multiple tissues with varying expression levels; particularly strong in brain tissue samples

  Overexpressed SF1 detection:

  • Higher signal-to-noise ratio due to increased target abundance

  • May require higher antibody dilutions (1:1000-1:3000) to prevent signal saturation

  • Can reveal additional bands at non-physiological expression levels

  Research from Liu et al. (2023) utilized both approaches when studying SF1's role in glucose homeostasis and beta cell function, showing that the antibody effectively detected both endogenous SF1 in lean mice (low expression) and the upregulated SF1 in non-diabetic obese mice .

  Sample Type	Recommended Dilution	Expected Signal Intensity	Notes
  Endogenous (normal tissue)	1:500 (WB)	Low to moderate	May require longer exposure
  Endogenous (high-expressing tissue)	1:1000 (WB)	Moderate	Brain, ovary tissue
  Transiently overexpressed	1:3000 (WB)	Strong	May show additional bands
  Stably overexpressed	1:1000-1:3000 (WB)	Moderate to strong	More physiological levels

Methodological Questions

• What are the optimal sample preparation protocols for different applications of SF1 (Ab-82) Antibody?

  Successful SF1 (Ab-82) Antibody application requires specific sample preparation protocols for each technique:

  Western Blot Sample Preparation:

  1. Lyse cells in RIPA buffer containing protease inhibitors and phosphatase inhibitors (critical for preserving phosphorylation state)

  2. Sonicate briefly to shear DNA and reduce sample viscosity

  3. Centrifuge at 14,000g for 15 minutes at 4°C

  4. Heat samples in reducing sample buffer at 95°C for 5 minutes

  5. Load 20-30 μg total protein per lane for cell lysates

  Immunohistochemistry Sample Preparation:

  1. Fix tissues in 10% neutral buffered formalin for 24-48 hours

  2. Process and embed in paraffin

  3. Section at 4-5 μm thickness

  4. For antigen retrieval, use TE buffer at pH 9.0 (preferred) or citrate buffer at pH 6.0

  5. Apply peroxidase and protein blocking steps before antibody incubation

  Immunofluorescence Sample Preparation:

  1. Grow cells on coverslips to 70-80% confluence

  2. Fix with 4% paraformaldehyde for 15 minutes at room temperature

  3. Permeabilize with 0.1% Triton X-100 for 10 minutes

  4. Block with 5% normal serum in PBS for 1 hour

  5. Apply SF1 (Ab-82) Antibody at 1:100-1:500 dilution

  For all applications, include appropriate positive controls (HeLa or HepG2 cells for WB; mouse ovary tissue for IHC) .

• How should researchers troubleshoot non-specific binding or weak signal when using SF1 (Ab-82) Antibody?

  When encountering problems with SF1 (Ab-82) Antibody performance, systematic troubleshooting can identify and resolve issues:

  For Non-specific Binding:

  Problem	Possible Cause	Solution
  Multiple bands in WB	Cross-reactivity	Increase antibody dilution (1:1000-1:3000); optimize blocking buffer composition
  High background in IHC	Insufficient blocking	Extend blocking time; use 5% BSA instead of serum; include 0.1% Tween-20 in wash buffer
  Non-nuclear staining in IF	Fixation issues	Optimize fixation protocol; use freshly prepared fixative; reduce permeabilization time
  Unexpected tissue reactivity	Epitope similarity in other proteins	Perform peptide competition assay with immunizing peptide; validate with knockout controls

  For Weak Signal:

  Problem	Possible Cause	Solution
  No band in WB	Low expression level	Increase protein loading; reduce antibody dilution (1:500); use enhanced chemiluminescence substrate
  Weak staining in IHC	Inadequate antigen retrieval	Try alternative retrieval method (TE buffer pH 9.0 instead of citrate) ; extend retrieval time
  Faint signal in IF	Low target abundance	Reduce antibody dilution (1:100); extend primary antibody incubation to overnight at 4°C
  Signal degradation	Improper storage	Store antibody at -20°C with 50% glycerol ; avoid repeated freeze-thaw cycles

  Additionally, researchers should note that SF1 expression varies significantly between tissues and physiological states. For example, SF1 is barely detectable in pancreatic beta cells of lean mice but highly expressed in non-diabetic obese mice , which could explain apparent "false negatives" in certain samples.

• What strategies can enhance the detection sensitivity of low-abundance SF1 in challenging samples?

  Detecting low-abundance SF1 protein requires specialized techniques to amplify signal while maintaining specificity:

  Western Blot Sensitivity Enhancement:

  1. Implement protein enrichment through immunoprecipitation before WB

  2. Use high-sensitivity ECL substrates with longer exposure times

  3. Transfer to low-autofluorescence PVDF membranes

  4. Apply signal amplification systems like biotin-streptavidin

  5. Reduce antibody dilution to 1:500 and incubate overnight at 4°C

  Immunohistochemistry Signal Amplification:

  1. Utilize polymer-based detection systems rather than traditional ABC methods

  2. Employ tyramide signal amplification (TSA) to enhance chromogenic signal

  3. Extend primary antibody incubation to 48 hours at 4°C

  4. Use automated IHC platforms with optimized protocols

  5. Consider antigen retrieval with TE buffer at pH 9.0 as specifically recommended for SF1

  Immunofluorescence Sensitivity Improvement:

  1. Apply fluorophore-conjugated secondary antibodies with bright, photostable dyes

  2. Use confocal microscopy with appropriate filter settings

  3. Implement deconvolution algorithms during image processing

  4. Reduce background through careful blocking and washing steps

  5. Consider using proximity ligation assay (PLA) for detecting SF1 interactions

  Research by Liu et al. demonstrated that optimized IHC protocols could detect the normally low SF1 expression in pancreatic beta cells, showing its upregulation in obesity contexts . This highlights the importance of technique optimization for physiologically relevant SF1 detection.

• How can researchers validate the specificity of SF1 (Ab-82) Antibody results in their experimental system?

  Rigorous validation ensures that observed signals genuinely represent SF1 protein:

  Genetic Validation Approaches:

  1. Compare wild-type samples with SF1 knockout/knockdown controls

  2. Analyze samples with known differential expression (e.g., obese vs. diabetic mice as in Liu et al. )

  3. Assess correlation between protein detection and mRNA levels via RT-qPCR

  Biochemical Validation Methods:

  1. Peptide competition assay using the immunizing peptide (S-P-SP-P-E)

  2. Compare with alternative antibodies targeting different SF1 epitopes

  3. Immunoprecipitation followed by mass spectrometry identification

  Technical Controls:

  1. Include isotype control antibodies to assess non-specific binding

  2. Test cross-reactivity against recombinant proteins of similar sequence

  3. Verify the molecular weight of detected bands (65-71 kDa for SF1)

  Application-Specific Validation:

  • For Western Blot: Run positive controls (HeLa, HepG2 cells) alongside experimental samples

  • For IHC: Include positive control tissues (mouse ovary) and negative control sections (primary antibody omitted)

  • For IF: Confirm nuclear localization pattern consistent with SF1's known subcellular distribution

  Liu et al. provided an excellent validation example by confirming SF1 expression using both immunofluorescence and in situ hybridization (RNAscope), demonstrating concordance between protein and mRNA detection .

Advanced Research Applications

• How is SF1 (Ab-82) Antibody being used in studies of metabolic disorders and what methodological considerations are important?

  Recent research has revealed SF1's role in metabolic regulation, particularly in obesity and diabetes:

  Key Research Applications:

  • Liu et al. (2023) demonstrated that SF1 expression in pancreatic beta cells protects against obesity-induced glucose intolerance by improving glucose-stimulated insulin secretion (GSIS)

  • SF1 was highly expressed in beta cells of non-diabetic obese mice and humans but decreased in diabetic subjects

  Methodological Considerations:

  1. Tissue-specific detection: SF1 expression can be transient and context-dependent, requiring precise timing of sample collection

  2. Comparative analysis: Parallel analysis of lean, obese non-diabetic, and diabetic samples is critical

  3. Cellular resolution: Single-cell approaches or careful co-staining with cell-type markers (e.g., insulin for beta cells) is necessary

  4. Functional correlation: Correlate SF1 detection with functional assays like glucose tolerance tests

  Experimental Design for Metabolic Studies:

  Study Objective	Recommended Approach	Key Controls	Notes
  SF1 expression in obesity	IHC/IF on pancreatic sections	Lean and diabetic samples	Use co-staining with insulin
  Temporal dynamics	Time-course analysis	Multiple time points	Critical for understanding progression
  Cellular specificity	Single-cell analysis or FACS	Cell-type markers	Avoids averaging across populations
  Functional significance	Correlate with GTT results	Age/weight-matched controls	Connect molecular to physiological data

  When studying SF1 in metabolic contexts, researchers should pay special attention to the physiological state of the animals/subjects and carefully document parameters like feeding status, age, and glucose levels that can influence SF1 expression .

• What are the critical differences in protocol when using SF1 (Ab-82) Antibody for phosphorylation status studies?

  When investigating SF1 phosphorylation, researchers must modify standard protocols to preserve phosphorylation status:

  Sample Preparation Modifications:

  1. Include phosphatase inhibitors (sodium fluoride, sodium orthovanadate, and β-glycerophosphate) in all buffers

  2. Maintain samples at 4°C throughout processing

  3. Avoid extended storage of samples before analysis

  4. Process samples quickly to minimize endogenous phosphatase activity

  Experimental Design for Phosphorylation Studies:

  Objective	Approach	Controls	Notes
  Comparative phosphorylation	Parallel detection with total and phospho-specific antibodies	Lambda phosphatase-treated samples	Calculate phospho/total ratio
  Signaling dynamics	Time-course after stimulus	Unstimulated control	Capture rapid phosphorylation changes
  Pathway analysis	Inhibitor treatments	Vehicle control	Determine upstream kinases

  Technical Considerations:

  1. For Western blot, run duplicate gels for total (SF1 Ab-82) and phospho-specific antibodies

  2. In IF/IHC applications, sequential or simultaneous staining may be required

  3. Include phosphorylation-positive controls (e.g., stimulated cell lysates)

  The SF1 (Ab-82) Antibody specifically targets a non-phosphorylated epitope around Ser82 , making it suitable for total protein detection regardless of phosphorylation state. This feature allows researchers to calculate the ratio of phosphorylated to total protein when used alongside phospho-specific antibodies.

• How can SF1 (Ab-82) Antibody be incorporated into advanced protein interaction studies?

  SF1 protein functions within complex molecular networks, and the SF1 (Ab-82) Antibody can be adapted for studying these interactions:

  Co-immunoprecipitation (Co-IP) Protocol:

  1. Lyse cells in non-denaturing buffer (e.g., 25 mM Tris-HCl pH 7.4, 150 mM NaCl, 1 mM EDTA, 1% NP-40, 5% glycerol)

  2. Pre-clear lysate with Protein A/G beads

  3. Incubate with SF1 (Ab-82) Antibody at 1:50 dilution overnight at 4°C

  4. Add Protein A/G beads for 2-4 hours

  5. Wash extensively and elute for analysis of interacting proteins

  Chromatin Immunoprecipitation (ChIP) Applications:
  Though not specifically validated for ChIP in the provided sources, researchers can adapt the antibody with the following considerations:

  1. Use mild crosslinking conditions (1% formaldehyde for 10 minutes)

  2. Sonicate chromatin to 200-500 bp fragments

  3. Optimize antibody amount (typically 2-5 μg per reaction)

  4. Include appropriate positive and negative control regions

  Proximity Ligation Assay (PLA) Protocol:

  1. Fix and permeabilize cells as for standard IF

  2. Incubate with SF1 (Ab-82) Antibody (1:100) and antibody against potential interactor

  3. Apply PLA probes and follow manufacturer's protocol for detection

  4. Include controls: single primary antibodies and known interacting proteins

  Bimolecular Fluorescence Complementation (BiFC):
  For detecting protein-protein interactions in living cells:

  1. Generate fusion constructs of SF1 and potential interactors with split fluorescent protein fragments

  2. Validate expression using SF1 (Ab-82) Antibody by Western blot

  3. Analyze interaction by fluorescence microscopy

  4. Use SF1 (Ab-82) Antibody in fixed cells to confirm proper localization