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Sunday, 9 November 2014

TE buffer (Tris-EDTA buffer) Recipe

The purpose of TE buffer is to solubilize DNA or RNA, while protecting it from degradation.

10 mM Tris, bring to pH 8.0 with HCl, 1 mM EDTA

A stock can be prepared and stored at RT

Component For 500ml
1M Tris pH 8* 5ml
0.5M EDTA pH 8 1ml
dH2O 496ml

Autoclave to sterilize. It is then best to remove a working aliquot and not repeatedly access the stock.
*the pH is usually adjusted to RNA 8.0 for DNA and 7.5 for

How to make acetate-acetic acid buffer solutions

Sodium acetate-acetic acid buffer solutions, pH 3.7-5.6

Sodium acetate trihydrate, CH3COONa.3H2O, M.Wt. 136.09;
0.2M solution contains 27.22g/l.
Acetic acid, glacial is ~17.47M.

x ml 0.2M NaOAc and y ml 0.2M HOAc mixed.

pH, 18°C X mL

0.2M NaOAc

Y mL

0.2M HOAc
3.7 10.0 90.0
3.8 12.0 88.0
4.0 18.0 82.0
4.2 26.5 73.5
4.4 37.0 63.0
4.6 49.0 51.0
4.8 59.0 41.0
5.0 70.0 30.0
5.2 79.0 21.0
5.4 86.0 14.0
5.6 91.0 9.0

Sunday, 11 May 2014

How to make 1x buffer from 20x

As explained before here it is very simple and you need to understand the concept.
or you can use the formula M1V1=M2V2


You have 20x Orange Juice and you wanna make 10 ml of 1x.

Simple use M1V1=M2V2

M1= Original Concentration [which is 20x]
V1= required volume to make 1x

M2= Desired Concentration [which is 1x]
V2= Desired volume which is 10 ml

20x * V1 = 1x * 10ml

V1= 0.5 ml of 20x concentrated juice is needed to add in 9.5 ml of water [10-0.5=9.5 ml]


Don't add 0.5 ml in 10 ml. This will make final volume 10.5 ml and your concentration will be wrong. 

How to make 1x BSA

How to make 1x bsa or Bovine serum albumin (BSA)

1x BSA generally suggest that you want  make 1 gram per litre BSA solution.

You can use the following method to make

Phosphate buffered

saline (PBS), pH 7.4,  10X None PS00000041 10X 50 ml 1X
Sigma-Aldrich A4919 Powder 0.5 g 1 g/L 


1. Weigh 0.5 g BSA and add to 300 ml purified water in a 600-ml beaker.
2. Add 50 ml of 10X PBS.
3. Adjust volume to 500 ml.
4. Store at room temperature in an appropriately labeled glass bottle.

How to make 1x buffer from 10x

This is very simple

You just need to learn the concept.

10x means 10 times concentrated

you need to make 1x

so you need to dilute it 10 time.

of you can take 1 part of 10x and mix with 9 part of water [1+9=10] to make 10x buffer.

Or you can use formula below make 1x buffer from 10x concentration buffer


M1 = stock concentration [10x]
V1 = volume needed of M1 concentrated stock [Z]

M2 = desired concentration [1x]
V2 = desired volume [say 10 ml you wanna make]

So as per M1V1=M2V2

10x * Zml = 1x *10ml

Z =1ml of 10x you need in 10ml of water.

This also means you need to add 10-1=9 ml of water in 1 ml of 10x concentrate to make 1x buffer.


Don't add 1ml in to 10 ml. which would be 11 ml and your concentration will be wrong.

Saturday, 4 February 2012

How to Dilute a Stock Solution

How to Dilute a Stock Solution

A. Why dilute? 

Here are two situations that arise repeatedly in molecular biology labs:
1. You have a stock solution of some compound,  let’s say an antibiotic, and you want to add the
compound to growth medium, at a much smaller concentration than the stock solution.
2. You have a tube of very concentrated bacteria, perhaps a billion cells per milliliter. You want to put
a few hundred of them on a petri plate, so that the colonies that arise will be easily distinguishable.
In both cases, the way out of the problem is to dilute the original solution. If you work in a lab, you need to
know how to do this.

B. Methods of calculating dilutions 

1. DILUTION FACTOR METHOD (fast, but requires inspiration): First, figure out the factor by which the
original solution must be diluted. Second, divide the final volume of the desired solution by that
factor, yielding the volume required of the original solution.
EXAMPLE: Suppose you need to make a 3 ml solution of growth medium supplemented with 50 µM of
the antibiotic ampicillin from a stock solution of 5 mM ampicillin. The dilution factor is :
  (5 mM) / (50 µM) = (5000 µM) / 50 µM) = 100
 so you need to dilute:
   (3 ml) / 100 = (3000 µl) / 100 = 30 µl
 of the stock solution to a final volume of 3 ml.

Sunday, 25 December 2011

Isolation of Casein from Milk

  Isolation and Identification of Casein From Milk Course Notes

Milk is the probably the most nutritionally complete food found in nature. Whole milk contains vitamins (principally thiamine,riboflavin, panthothenic acid and vitamins A, B12 and D), minerals (calcium, sodium, phosphorus, potassium, and trace minerals), proteins (which include all the essential amino acids), carbohydrates (mostly lactose), and lipids (fats). Whole milk is an oil in water emulsion, containing approximately 4% fat dispersed as very small (micron sized) globules. The fat emulsion is stabilized by complex phospholipids and proteins that are absorbed on the surface of the emulsion. Since the fat in milk is so finely dispersed it is more easily digested than fats from any other source.

Isolation of Casein, Lactose, and Albumin from Milk

Milk is a food of exceptional interest. Not only is milk an excellent food for the very young, but humans 
have also adapted milk, specifically cow’s milk, as a food substance for persons of all ages. Many 

specialized milk products like cheese, yogurt, butter, and ice cream are staples of our diet.

Experiment 11: Isolation and Characterization of Casein from Milk

Adapted from Experiment 21, “Isolation of Protein, Carbohydrate and Fat from Milk”, in
Mohr. S.C., Griffin, S.F., and Gensler, W. J. Laboratory Manual for Fundamentals of
Organic and Biological Chemistry by John McMurry and Mary E. Castellion,: nglewood
Cliffs, Prentice-Hall, 1994 and Wayne P. Anderson (4/2002)

Purpose: In this lab you will be isolating the proteins casein and lactalbumin from a sample of milk. You
will use these values to determine the percent protein in milk compared to the listed value on the box.


Science Protocols