1) If direct stains work so well, why would we ever use indirect stains? Give two reasons why you might choose to use indirect stains instead of direct stains?  2) Assume that two days (dye A and dye B) were applied to bacterial smear. The cells were stained by dye A while the slide background was stained with dye B. Which stain had an anionic chromogen? Which stain had a cationic chromogen?

define the term multicolor banding,

What is the charge of the chromophore/colored ion of the positive staining and negative staining?

A.Why do you plate the cells from the viable count on LB agar without ampicillin? B.If you observe 100 colonies on your 1/100 plate, how many colonies do you expect if everything works perfectly on your 1/1000 plate?

You overexpressed (asked bacteria to make a lot of) an 80 kDa protein carrying a 6X-His tag and purified it on a nickel column. You collect frac ons from your purifica on and analyze them using SDSPAGE. The results are shown in image attached.  a) Interpret the results from the gel. What is wrong? (see image attached) b) Identify 2 possible reasons why this problem is occurring, and for each reason, suggest an experimental modifica on you can do to troubleshoot.

Which of the following technique is FALSE in microscopy? Osmium tetroxide can be used as a fixative as well as a negative stain in transmission electron microscopy. Two proteins; each tagged with their individual primary antibody followed by one protein with rhodamine conjugated secondary antibody and the other with fluorescein-conjugated secondary antibody can be visualized simultaneously using a fluorescence microscope. The emission spectrum of Rhodamine is 580 nm The emission spectrum of Fluorescein is 521 nm O An objective lens with 100X magnification and projection lens with 10X magnification is going to produce a 1000X total magnification. Phase contrast and differential interference contrast (DIC) do not require staining.

What is the experimental procedure illustrated in the figure above?  What label (1-3 words) would you write next to each of the 5 arrows in the procedure? )  Briefly write a concise but complete description of the figure closely following the labels you have used in your answer to the second part of the question.