Question

You are given a stock solution of ribosylated collagen. In order to complete your experiment, you will need four 1ml aliquots of ribosylated collagen in phosphate buffered saline (1M), each containing 67.5 ng/ml. The stock concentration is 10 ug/ml, What steps are required to achieve the required concentrations? During lab a classmate accidentally breaks an Erlenmeyer flask: a single shard causes a 50mm laceration between his elbow and wrist. You decide that the best way to keep the wound clean is to wash it with saline before applying a bandage. Unfortunately, the only available products are sterilized table salt (NaCl) and water. Make a 0.8% saline solution in order to protect your friends arm from infection. You are processing your primary hippocampal neurons for ultramicrotomy: currently you are performing an ascending dehydration series in ethanol (EtOH) The next step requires 30% ethanol in water. You have only 95% EtOH and an unlimited supply of water. How would you make 100mlof 30% EtOH? In order to prepare your Candida albicans yeast for ultrastructural analysis, you need to chemically fix them with 200 ml of paraformaldehyde and glutaraldehyde in Sorenson's phosphate buffer. Since this will be a morphological assessment, you decide that the appropriate concentrations will be 4% and 2.5% respectively. The paraformaldehyde is solid (w/v), while glutaraldehyde is liquid (v/v) and is delivered in a stock concentration of 25%. How can you do this? How would you make 1 M NaCl? The molecular weight of NaCl is 58.44. How would you make 15 mM NaCl in 200 ml of water from stock?

Answer 1

1. A portion of the stock has to be diluted for this purpose. We could take the required amount and then volume could be made up with Phosphate buffered saline.

10 microgram or 10000ng is present in 1000 microlitre (1ml)

then 67.5 ng will be present in 1000/ 10000 multiplied with 67.5

= 6.75microlitres

6.75microlitres from the stock has to be taken and PBS will be added to make up the volume 1ml.

2. 0.8g of NaCl has to be added to 100ml of sterilized water

3. Suppose, if we start with 100ml of 90% alcohol, we have to tkae 31.5ml of alcohol from it and water could be added to make up the volume to be 100ml, and the resulting solution will be of 30% concentration, i.e we wiill have 100ml of 30% alcohol.

4. for 4 making 4% paraformaldehyde, we have to take 8 grams of paraformaldehyde in 100ml of the buffer.The, glutaraldehyde has to be diluted 10 times from the stock solution with the buffer.