Question

1. What would be the concentration of a 16 mM solution after 4–fold dilution?

2. To make 100 mL of a 5% (w/v) glucose solution, how much glucose would you use?

3. How much NaCl would you add to make an aqueous 10% (w/v) NaCl solution with a final volume of 500 mL?

A 1X reaction buffer contains the following concentrations of each compound. Calculate the amount of each compound (in g) that would be needed to make 100 mL of a 5x stock solution.

Compound	Conc. 1x soln.	Conc. 5x soln.	Molecular Weight	Grams to Add (for 100 mL final)
A	0.5 M		200
B	0.2 M		350

You have a protein sample at a concentration of 50 mg/mL. You make a 1:5 dilution of this sample and then take out a 200 µL aliquot. How many mg of protein are contained in this aliquot?

You are digesting an unknown plasmid with the restriction enzyme MboII. Use the table below to calculate how much of each component you need to add to your digest for a final volume of 20 µL.

Component	Stock Conc.	Desired Amount in Reaction	Volume of Stock to Add (for 20 µL reaction)
Plasmid	1 mg/mL	1 µg
MboII enzyme	5 U/µL	15 U
Buffer	4x	1x
Water	---	---
		Total Volume:	20 µL

Answer 1

Question:

(a) Conc. 16 mM

Dilution = 4 fold

Final conc. = initial conc/dilution

= 16/4= 4 Mm

(b) 5% (w/v)

Volume = 100 ml

= 5g of glucose in 100 ml

(c) 10% (w/v)

= 10 g in 100 ml

Volume = 500ml

So, 10*500/100 = 50g NaCl in 500 Ml

(d) Compound A = 0.5 M

M.W = 200

Compound B = 0.2 M

M.W = 350

For 5x stock

Compound A = 0.5*5= 2.5 M

1M = 200g in 1000 ml OR 20 g in 100 ml

2.5 M = 20*2.5 = 50 g in 100 Ml

Compound B = 0.2*5 = 1M

1M = 35g in 100 ml

Compound A- Conc. 2.5M and gram added = 50g

Compound B- Conc. 1 M and gram added = 35g

(e) Concentration = 50 mg/ml

Dilution = 1:5

Final concentration = 50*1/5 = 10mg/ml

Amount in 200 µL or 0.2 ml = 10mg*0.2/1

= 2mg

(f) Plasmid: conc. 1 mg/mL or 1 µg/ µL,

So, take 1 µg of plasmid

Mboll enzyme = conc. 5 U/ µL

15 U in 3 µL

Buffer: initial: 4x

Volume of 1x to be added = 20-(1+3)

= 16 µL

So take 16/4 = 4 µL of 4x buffer

Water = 16-4 = 12 µL

Plasmid – 1 µL

Mboll enzyme - 3 µL

Buffer(4x) - 4 µL

Water = 12 µL