Solutions and Dilutions Basic Skills of the Biotechnology Workplace - - PowerPoint PPT Presentation

Solutions and Dilutions

Basic Skills of the Biotechnology Workplace

What do you know about solutions?

• Solute: the substance being dissolved
• Solvent: the substance that dissolves the

solute

• Concentration of a solution can be expressed

as the amount of mass per some unit of volume, for example, g/mL

Solution

Common Solution in Biotechnology Room Solution is Temperature Boiled Until Clear Agarose

Agarose Gel

Common Solution in Biotechnology

• Agarose solution is used to cast agarose gels

for electrophoresis

• 0.8% or 1% agarose solutions are commonly

used to cast gels for electrophoresis

• Agarose gels with higher concentrations (2%
• r 3%) are used to visualize very small pieces
• f DNA

Why is the concentration of the gel important?

• Incorrect concentrations make it difficult to

visualize DNA bands during electrophoresis

• Concentration of the gel affects the resolution

and separation of DNA fragments

Low Agarose Concentration High Agarose Concentration

Agarose Solution

• Solute: Agarose
• polysaccharide polymer extracted from

seaweed

• Solvent: Buffer (either TBE or TAE)
• near-neutral pH which allows the DNA to

migrate towards the anode (+)

Mass/Volume Concentration Equation

0.8% Agarose 100mL Total Volume

_____ g/mL x _____ mL = _____ g of solute

concentration volume to be weighed out, desired desired dissolved in the solvent

What do you know about dilutions?

Dilution

• Concentrated solutions are “diluted” by

adding more solvent

• Stock solutions need to be diluted to “working

concentrations”

Common Dilution in Biotechnology

• Diluting concentrated stock solutions of TBE

and TAE buffers used for gel electrophoresis

• Buffers resist changes in pH and help preserve

the structure and function of molecules dissolved in the buffer

TAE Buffer

• TAE buffer (Tris-acetate with EDTA) - used to

cast agarose gels and for running buffer during electrophoresis experiments

• Commonly shipped as 50X or 20X

concentrated

• “Working concentration” is 1X

Dilution Equation C1V1 = C2V2

C1 = concentration of the concentrated stock solution V1 = volume to use of the stock solution in the diluted sample C2 = desired concentration of the diluted sample V2 = desired volume of the diluted sample

C1V1 = C2V2

Dilute 50x TAE buffer to a working concentration of 1X 100 mL Total Volume

Casting an Agarose Gel Making Agarose