IV. User Supplied Reagents and Equipment: 96-well clear plate with flat bottom Microplate reader
V. Storage and Handling: Store kit at -20°C, protected from light. Avoid repeated freeze/thaw for all non-buffer components. Briefly centrifuge small vials prior to opening. Read the entire protocol before performing the assay.
VI. Reagent Preparation & Storage Tyrosinase Substrate: Dissolve the lyophilized tyrosinase substrate in 220 μl ddH2O. Use within two months. Keep on ice while in use. Tyrosinase: Dissolve the lyophilized tyrosinase in 220 μl Tyrosinase Assay Buffer. Aliquot and store at -20°C. Avoid repeated freeze/thaw cycles. Use within two months. Keep on ice while in use. Tyrosinase Enhancer: Ready to use. Protect from light. Keep at room temperature while in use. Inhibitor Control (Kojic Acid): Add 75 µl of ddH2O to make a stock solution of 10 mM Kojic Acid. Mix well. Make a 0.75 mM working solution of Kojic Acid by adding 92.5 µl of ddH2O to 7.5 µl of 10 mM Kojic Acid Stock solution. Use within two months.
VII. Tyrosinase Inhibitor Screening Protocol: 1. Screening compounds, Inhibitor control and Blank Control Preparations: Dissolve test inhibitors into proper solvent. Dilute to 5X the desired test concentration with Tyrosinase Assay Buffer before use. Add 20 μl diluted test inhibitors, Inhibitor Control working solution, or Tyrosinase Assay Buffer into wells assigned as test inhibitors (Sample, S), Inhibitor Control (IC), or Tyrosinase Enzyme Control (EC) wells, respectively. Additional wells with serial dilutions of the test inhibitors may be prepared at this time if desired, containing 20 µl in each candidate well. Note: Preferred final solvent concentration should not be more than 5% by volume. If solvent exceeds 5% include a Solvent Control to test the effect of the solvent on enzyme activity. 2. Tyrosinase Enzyme Solution Preparation: For each well, prepare 50 μl Tyrosinase Enzyme Solution. 48 μl Tyrosinase Assay Buffer 2 μl Tyrosinase Mix well & add 50 μl/well into wells containing test inhibitors, Inhibitor Control & Enzyme Control. Mix. Incubate for 10 min. at 25ºC. 3. Tyrosinase Substrate solution preparation: For each well, prepare 30 µl of Tyrosinase Substrate solution 23 μl Tyrosinase Assay Buffer 2 μl Tyrosinase Substrate 5 µl Tyrosinase Enhancer Mix and add 30 μl of Tyrosinase Substrate Solution into each well. Mix well. 4. Measurement: Measure the absorbance in kinetic mode for 30-60 min. at 510 nm. Choose two time points (T1 & T2) in the linear range of the plot and obtain the corresponding values for the Absorbance (Abs1 and Abs2). 5. Calculations: Calculate the slope for all samples, including Enzyme Activity Control (EC), by dividing the net ΔAbs (Abs2- Abs1) values by the time ΔT (T2-T1). Calculate % Relative Inhibition as follows:
II
IV. User Supplied Reagents and Equipment: 96-well clear plate with flat bottom Microplate reader V. Storage and Handling: Store kit at -20°C, protected from light. Avoid repeated freeze/thaw for all non-buffer components. Briefly centrifuge small vials prior to opening. Read the entire protocol before performing the assay. VI. Reagent Preparation & Storage Tyrosinase Substrate: Dissolve the lyophilized tyrosinase substrate in 220 μl ddH2O. Use within two months. Keep on ice while in use. Tyrosinase: Dissolve the lyophilized tyrosinase in 220 μl Tyrosinase Assay Buffer. Aliquot and store at -20°C. Avoid repeated freeze/thaw cycles. Use within two months. Keep on ice while in use. Tyrosinase Enhancer: Ready to use. Protect from light. Keep at room temperature while in use. Inhibitor Control (Kojic Acid): Add 75 µl of ddH2O to make a stock solution of 10 mM Kojic Acid. Mix well. Make a 0.75 mM working solution of Kojic Acid by adding 92.5 µl of ddH2O to 7.5 µl of 10 mM Kojic Acid Stock solution. Use within two months. VII. Tyrosinase Inhibitor Screening Protocol: 1. Screening compounds, Inhibitor control and Blank Control Preparations: Dissolve test inhibitors into proper solvent. Dilute to 5X the desired test concentration with Tyrosinase Assay Buffer before use. Add 20 μl diluted test inhibitors, Inhibitor Control working solution, or Tyrosinase Assay Buffer into wells assigned as test inhibitors (Sample, S), Inhibitor Control (IC), or Tyrosinase Enzyme Control (EC) wells, respectively. Additional wells with serial dilutions of the test inhibitors may be prepared at this time if desired, containing 20 µl in each candidate well. Note: Preferred final solvent concentration should not be more than 5% by volume. If solvent exceeds 5% include a Solvent Control to test the effect of the solvent on enzyme activity. 2. Tyrosinase Enzyme Solution Preparation: For each well, prepare 50 μl Tyrosinase Enzyme Solution. 48 μl Tyrosinase Assay Buffer 2 μl Tyrosinase Mix well & add 50 μl/well into wells containing test inhibitors, Inhibitor Control & Enzyme Control. Mix. Incubate for 10 min. at 25ºC. 3. Tyrosinase Substrate solution preparation: For each well, prepare 30 µl of Tyrosinase Substrate solution 23 μl Tyrosinase Assay Buffer 2 μl Tyrosinase Substrate 5 µl Tyrosinase Enhancer Mix and add 30 μl of Tyrosinase Substrate Solution into each well. Mix well. 4. Measurement: Measure the absorbance in kinetic mode for 30-60 min. at 510 nm. Choose two time points (T1 & T2) in the linear range of the plot and obtain the corresponding values for the Absorbance (Abs1 and Abs2). 5. Calculations: Calculate the slope for all samples, including Enzyme Activity Control (EC), by dividing the net ΔAbs (Abs2- Abs1) values by the time ΔT (T2-T1). Calculate % Relative Inhibition as follows:II
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