From owner-drosophila@net.bio.net Fri Feb 17 22:00:00 1995 Newsgroups: bionet.drosophila Path: biosci!bcm!cs.utexas.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!uchinews!kimbark!mg16 From: mg16@kimbark.uchicago.edu (Mark D. Garfinkel) Subject: Re: Correction: Transformation Volume X-Nntp-Posting-Host: midway.uchicago.edu Message-ID: Sender: news@midway.uchicago.edu (News Administrator) Reply-To: mg16@midway.uchicago.edu Organization: ClonUS, Inc., Hyde Park Division References: Date: Sat, 18 Feb 1995 15:21:03 GMT Lines: 43 In article , Stephen Hall wrote: >Earlier I posted a reply that 1% of egg volume or 100 nl was >appropriate. Actually, the egg volume is 10 x 10E-15 liters >which makes the amount injected considerably less. My apologies. Gasp! This is like the Everett Dirksen line about "a billion here, a billion there, and pretty soon you're talking about real money." Yes, Ashburner's Big Grey Book, page 216, says an embryo has a volume of 10e-14 liter, but the same sentence says the *water* weight of an embryo is 7.3 ug. Given that we're dealing with standard temperatures & pressures, one can safely assume that the water content is at/near unit-density, i.e., 1 gram per milliliter. Thus, the water content can account for 7.3 nl all by itself. Add in ca. 2 ug of protein, at a typical density of 1.4 g/ml, and that's another 1.4 nl. So, from chemical first principles we arrive at a volume close to 10 nl, not 10 fl. Six orders of magnitude is nothing to sneeze at. With all due respect to Michael, this is commonly referred to as a "mistake." Given the roughly ellipsoidal dimensions of an egg/embryo, major axis of 500 um and two minor axes of ca. 175 um -- one calculates an egg volume of 16 nl [(4*pi/3)*abc, where a,b,c are the half-axis values]. Thus, Ashburner's Grey Book page 216 linear dimensions of an egg, plus a bit of geometry, give a volume consistent with the above biochemical calculation. As for injection volumes, see also Big Grey Book page 223, where 1-100 picoliters is given as the practical range. For an egg volume of ca. 10 nl, the higher injection volume is 1% of total egg volume. This rule of thumb dates back to the initial Spradling & Rubin (1982) P factor transformation paper, and probably to the Van Deusen (1976) cell trans- plantation paper upon which their injection methods were based. BTW, lest anyone forget: "nano" is the prefix for 10e-9, "pico" for 10e-12, "femto" for 10e-15, "atto" for 10e-18, and "decca" for record labels. Mark -- Mark D. Garfinkel (e-mail: garfinkl@iitmax.acc.iit.edu) My views are my own, which is why they're copyright 1995 (c) Note that uchicago.edu newsfeed is terribly slow these days .