Well, you can add to your list Silver sulfadiazine, mercurochrome, and merthiolate, all OTC antiseptics. The mercurochrome, since it contains Br, might be used as another standard for the Br edge.
JPK -----Original Message----- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of James Holton Sent: Tuesday, September 12, 2017 1:46 PM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Risk assessment for heavy atom soaking - examples? One more correction, It seems brominated vegetable oil (BMO) really does contain Br atoms! I could have sworn I read in some reputable source long ago that the process of "bromination" was an old term for general reduction of double bonds and did not necessarily involve bromine. Usually hydrogen. I remembered this because I thought it was hugely counter-intuitive. Now, of course, I cannot find that reference. So, who am I to pit the validity of my memory against Wikipedia and a long list of links to health-nut web blogs? Guess I was wrong about that. The Mountain Dew I am drinking right now has a very faint X-ray fluorescence peak that could be Br. Hard to be sure above background. So I will have to get a sample of neat BMO to sit next to my shampoo, pepto and sunscreen on my shelf of heavy atom compounds that are on the FDA's GRAS list: https://www.fda.gov/food/ingredientspackaginglabeling/gras/ Remarkably, the MSDS for BMO is less scary than that of ordinary vegetable oil. This raises more than one interesting topic, but the most relevant here I think is "bio-availability". Selenomethionine is much much more bioavailable than selenium sulfide, which is the active ingredient in my dandruff shampoo. Apparently, humans don't absorb it, but microorganisms can mistake it for a source of sulfur. I expect the bio-availability of Hg in pizza is pretty high considering how it bio-amplifies in fish, so I stand by my APE. But it is always prudent to read the MSDS before you open a bottle, and then read the MSDS of something similar just to put it in perspective. -James Holton MAD Scientist On 9/6/2017 12:59 PM, James Holton wrote: > Was just pointed out to me off-list that my anchovy data was off, so I > just double-checked the FDA website: > > https://www.fda.gov/food/foodborneillnesscontaminants/metals/ucm115644 > .htm > > > Turns out the latest number for anchovies is 0.016 ppm, or 0.5 ug per > ounce (28g). > > So, if you use a whole 2 oz can, that's still ~ 1 microgram Hg as the > Anchovie Pizza Equivalent. > > And it looks like one piece of bigeye tuna sushi could be as much as > ~14g*1.816ppm = 25 APEs > > -James Holton > MAD Scientist > > On 9/6/2017 11:44 AM, James Holton wrote: >> Something that could perhaps be of use here is what I like to call >> the "Anchovie Pizza Equivalent" (APE), which is about 1 microgram of >> mercury. According to the Food and Drug Administration website here >> in the USA the average mercury content of anchovies is 0.34 ppm, >> which is about 1 microgram per ounce of fish. Tuna can be higher, >> but varies a lot from fish to fish. My point here is that most >> institutions regard the amount of mercury you bring onsite for >> purposes of eating for lunch, be it sushi or pizza, as small enough >> to be negligible. I tend to agree. So, one could argue that 1 >> microgram of Hg per day is a "safe amount". Especially if you don't >> eat it. >> >> In terms of protein crystals, a 100 micron wide cube has a volume of >> 1 nanoliter, and if it were soaked to a final concentration of 50 mM >> Hg that is 1e-9 L * 50e-3 mol/L *200 g/mol = 10 ng. So, 100 protein >> crystals soaked with Hg add up to roughly 1 APE. Please note that I >> am in no way encouraging you to eat your protein crystals, and >> especially not the solutions you soak them in. You should do your >> own APE calculations for those. But I do think it important to note >> just how tiny the amount of metal in our crystals really is. >> >> Now, mercury is purportedly the second-most-toxic metal after >> Plutonium. But Pu derivatives are uncommon. In fact, until recently >> (4zhd) Pu derivatives were unheard of. The authors I'm sure will tell >> you 4zhd involved no small amount of paperwork. But as long as you >> are not working with Pu, you can regard every other metal as less >> toxic than Hg. >> >> Another good example is selenium; by far the most common metal >> derivative. Although toxic, Se is also a dietary requirement. I >> suppose this is an excellent demonstration of what "moderation" >> really means. The Recommended Daily Allowance (RDA) of selenium in >> the USA for adult men and pregnant women is 55-60 micrograms per day. >> In crystals, one Se atom per 100 amino acids at 50% solvent comes to >> an overall concentration of 50 mM. So, a 100 micron crystal contains >> about 4 ng of Se. It would take 15,000 such crystals to add up to >> the US RDA. The synchrotrons I work at don't go thought that many >> crystals every day. But even if they did, I'd stick to my >> commercially available multivitamin to get my dietary selenium. >> >> So, although it is never a good idea to be sloppy with chemicals in >> the lab, I think it is also important to do the math and think about >> not just the toxicity of the things we work with on the bench, but >> the everyday items all around us. It is never a good idea to be >> antagonistic with regulators about such things. They are only trying >> to do their job, and all they are trained to know about are LD50s and >> how to stay as far below them as possible. A little >> gently-pointed-out insight into non-lethal applications of heavy >> metals can be helpful all around. The over-the-counter drug Pepto >> Bismol (bismuth subsalicylate) is almost 50% bismuth by weight, a >> metal that is right next to mercury on the periodic table. Brominated >> vegetable oil contains no bromine, by the way. And dandruff shampoos >> such as Selsun Blue make an excellent and surprisingly radiation-hard >> reference for the selenium edge. >> >> -James Holton >> MAD Scientist >> >> On 9/4/2017 3:13 AM, Dr Stephen Graham wrote: >>> Hi all, >>> >>> (This email is aimed primarily at my UK colleagues, but feel free to >>> read on and gloat that you don't have to write safety forms in your >>> lab/country!). >>> >>> I need to sort out written risk assessments for heavy atom soaking >>> of crystals in my lab. I wondered whether anyone would be willing to >>> share the risk assessments they have in their institute/company so >>> that I can seek inspiration and make sure I'm keeping up with best >>> practice. >>> >>> Many thanks, >>> >>> Stephen >>>
