# User:Klare Lazor/Notebook/Chem-496-001/2012/02/07

Biomaterials Design Lab Main project page
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## Objective

• making buffer for tagging tom

## Description

• Use of a distant reporter group as evidence for a conformational change in a sensory receptor
• pH increases and deprotonates
• cysteine pka=8
• 3mg of 5-iodoacetamido fluorescien mw 515.3g/mol (4 Fold Excess)
• how much cysteine? mw= 121.16g/mol
• 35 cysteine in BSA

Caculations

• 35(121.16g/mol)= 4240.6 g/mol of cysteine
• (4240.6 g/mol of cysteine)/(67,000g/mol of BSA)= 0.06329 (mass ratio)
• (0.06329)*(0.00495 grams amount of BSA in stock)= 0.000313g/50mL of solution
• (0.000313g/50mL)/(121.16 g/mol)= 2.5E-6mol/mL
• (2.5E-6 mol/mL)/ (50mL)= 5.172E-7 mols of cysteine per mL solution
• Whatever mLs of BSA we use in sample(2.767mL) X 5.172E-7mols of cysteine per mL solution=0.000001 mols of cysteine
• To determine amount of 5-iodoacetamido fluorecien
• .000001 mols of cytiene x (4mol of dye/1 mol cysteine) x 515.3g/mol= 0.0029 grams of 5-iodoacetamido fluoreciene

Calculations for buffer Solution

• pka= 7.21 for phosphate
• ph=pka+log[salt]/[acid]
• 7.21=7.21 +log[salt]/[acid]
• [salt]/[acid]= 1
• so any concentration as long as they have a ratio of 1, we use 0.05mols/Liter
• may have to increase the amount of Na2HPO4 because it is hydrated
• 141.98g/mol Na2HPO4- * 0.050 mol/L = 7.099 g/L x .25 L =1.7747g (added extra 2 grams)
• 137.99g/mol x 0.05 mol/L = 6.89 x .25 L = 1.725 g
• total solution 250mL

Procedure

• mixed in 406 microliters of a pH buffer of 7.02, 2.9 mg of 5-iodoacetamido and 2.776 mL BSA from Stock
• Ideal ph is between 7 and 8
• after 2hours let reaction sit
• used a dialysis bag to separate the free gold and dye from solution

Whats going on

• Ph increases and deprotonates the cysteine, the deprotonated nitrogen(nucleophile) is then able to attack they carbonyl group of the 5-iodoactamido and attach.

## Notes

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