HPsensor 2

Guide
(The following is our recommended protocol. This protocol is for guidance only and should be modified according to your specific needs).

1. Stock Solution Preparation
1.1 Solvent: For most dyes, an organic solvent such as anhydrous DMSO is typically used for dissolution.
1.2 Concentration recommendation: It is generally recommended to prepare a high-concentration stock solution of 1-10 mM.

2. Working Solution Preparation
2.1 Diluent: Distilled water adjusted to pH 8 using 0.1 M NaOH; Carmody buffer is used for pH-dependent experiments.
2.2 Working concentration: 2 μM for general protein staining; 0.5 μM for surface hydrophobicity and binding affinity measurements; 1X, 3X, 10X relative to protein concentration for native PAGE experiments.
Note: Adjust working solution concentration as needed; prepare fresh before use.

3. Staining Procedure
3.1 Sample type: Purified protein samples (bovine serum albumin (BSA), myoglobin (Mb), apomyoglobin (ApoMb), beta-lactoglobulin (β-lg)).[1]
3.2 Incubation conditions:
3.2.1 For general protein staining: Incubate 2 μM HPsensor 2 with 2 μM protein (1:1 ratio) at room temperature for 1 hour.
3.2.2 For surface hydrophobicity and binding affinity measurements: Incubate 0.5 μM HPsensor 2 with protein samples at 25 °C for 1 hour.
3.2.3 For pH-dependent experiments: Incubate 0.5 μM HPsensor 2 with 0.1 μM heated/unheated protein in Carmody buffer (pH 3, 5, 7, or 9) at 25 °C for ~30 minutes.
3.2.4 For native PAGE: Incubate 2 μg protein with 1X, 3X, or 10X HPsensor 2 at room temperature for 1 hour.

4. Controls
4.1 Set up free dye control (HPsensor 2 without protein) to measure background fluorescence.
4.2 Set up protein-only control to subtract protein auto-fluorescence from experimental readings.
4.3 Set up ANS-stained protein control for comparative fluorescence signal analysis.

5. Detection & Analysis
5.1 Instrument: Fluorometer for fluorescence spectroscopy; gel imaging system for native PAGE analysis.
5.2 Ex/Em wavelength: Excitation at 528 nm, emission at 579 nm.
5.3 Result analysis:
5.3.1 Fluorescence intensity changes: HPsensor 2 shows weak fluorescence in aqueous solution, with significant fluorescence enhancement (up to 60-fold compared to ANS) when bound to hydrophobic protein surfaces (highest for BSA, followed by ApoMb, lowest for Mb).
5.3.2 Fluorescence localization: Binds to exposed hydrophobic surfaces of proteins.
5.3.3 Native PAGE results: HPsensor 2 exhibits stronger UV signal than ANS for protein bands, with signal intensity correlating with protein surface hydrophobicity.
5.3.4 pH and heat effect: Reduced fluorescence signal is observed at low pH and for heated (denatured) proteins, except for β-lg at pH 9.
5.3.5 Binding affinity: Dissociation constants (Kd) are 1.2 μM for Mb, 0.33 μM for ApoMb, and 0.034 μM for BSA.
5.3.6 Surface hydrophobicity (S0): Calculated as the slope of net relative fluorescence intensity vs protein concentration, with values of 2934 for Mb, 65212 for ApoMb, and 658608 for BSA.

MedChemExpress (MCE) has not independently confirmed the accuracy of these methods. They are for reference only.