Neil: good evening ladies and gentleman thanks all for coming out on this evening when there is a lot of competition with albert schazzenger speaking at the republican convention tonight . I congratulate you on your choice. Tonight we have a great lecture. This is Graham George who is in fact a defector from Slack. He was with s for 11 years at our laboratory here and then was lured away mysteriously to Canada where it is cold and wet all the time rather than <inaudible>. I’m not quite sure why he did that there must have been a good reason for that.
Tonight graham is going to talk to us I believe about metal and fish. I spend a lot of my time, wasted a lot of my time trying to get metal into fish in the form of hooks without much success in it. I hope may get some hints tonight. Let’s have a big round of applause for graham.
Graham: thank you very much Neil. Tonight the title of my talk is metals, molecules, life and death. I want to tell you about metals, how they crop up in molecules and how these are important in our lives and how they can sometimes cause death. What is a metal? Metals are very familiar they are all around us. This a picture of some stainless steel, a copper kettle, a coke can, a copper mug and some screws and we’re very familiar with them in our everyday lives. If you look very closely at a metal then you will see that pure metals are composed of one kind of atom. This is chemist styled rendition. These little balls imp going to be showing you, a fair number of are all atoms and the little lies between them are where they are joined together with what is called chemicals bonds, which means they us attach to each other.
as I said pure metals are composed of just one kind of atom and this what you might see if you looked with a very powerful structural tool but some of the metal in this copper mug you will see a whole bunch of individual copper atoms all bound teach other . They are all around and they can occur not only in pure metallic form but also in molecules. I’m going to come back and tell you what molecules are in a moment but first I’m going to tell you some sources of metals in our environment you can crudely divide them up.
One source of metals is natural sources. They occur in our environment through weathering of our rocks and minerals and they will be dissolved in natural waters, there are admitted by things called volcanoes, exotic metals in forms such as erratum penal fluoride, come out of the top of volcanoes, they also occur form manmade sources. There is a lot of interest in manmade sources of metal these days. Things like farming, organic farming metal is becoming important in that. Other man made sources include miming operations where things like arsenic are released into the environment in incredible quantities sometimes.
What are the sources of humid exposure to metals? Mainly from our food and our drinking water and these are usually beneficial and sometimes they are not, we’ll talk about that later. These are usually benefice sources some metals we really need and I say more about that. Often the bad sort of metal exposure is direct contact. You can see someone doing something a little unwise with a little bit of mercury.
Metals in humans, they have two basic roles they can fulfil. One is essential metals, we need metals to stay alive. It’s very important to us. most of us are at some time have taken vitamins or mineral supplements , you will often see things like copper , iron ,zinc , moletinum and selenium . We know that selenium is very important. I’m going to say at this point that I’ve been pretty generous in my definition of a metal. selenium is actually not a metal it’s something called a metalloid but metals , molecules , life and death sounded a lot better than metals, metalloids, life and death so I’ve been a little bit generous . That is really for any chemist who is in the audience. I’m counting things like arsenic and selenium as metals for the purpose of this talk.
There are other metals. Some of these have toxic effects and here are some well-known ones that do, arsenic, mercury, lead and cagnium. These have no know role in our bodies. arsenic may have, at the end I will answer questions but I can tell people the riles that arsenic might have at the end if they want to but I prefer that you didn’t ask questions during the talk. Mercury has no known role at all in biology, cranium might be very important in turns out in controlling global carbon dioxide and how much it is dissolved in the ocean. I’m not going to really say anything about that but it’s not important for us but it may be very important in our organism and just about any metal is toxic. If you take enough of it, it will do you harm.
As I mentioned earlier this is a flash back to a previous slide, metals are all around us they appear in metallic form but also molecules and these are the things I really want to talk about. what’s a molecule, this is picture of a molecule and again the little round balls are atoms and this in the idle is a copper metal atom and in this case if you remember that previous picture is showed we had copper bound to a whole load of other coppers in this case we have copper bound to three of these yellow atoms and these are sulphurs. it doesn’t really matter what they all are the point is this is a discreet entity, sits a discreet little unit , packet of material if you like in which different atoms are arranged and we call these things molecules.
How big are molecules? The length of the distance between the Couperin sulphur is about billions of an inch. These are pretty small things but they are very important as you see. Another example of a molecule occurs in us. Iron which is a metal as much of us know is essentially component of blood, it occurs in a protein called haemoglobin and here’s a picture of it. This is a cartoon representation where many of the atoms are drawn in this stylized ribbon, in fact there are lots of atoms all around if I drew every atom in the picture it would look confusing to you. The important part I have drawn properly and you can see in the middle here is the atom of iron bound to four nitrogens in what we call a hemi group and it’s very important. It’s the thing that does the moving around of oxygen in our bodies. This is an essential thing for us to stay alive. We need iron, we can’t live without it and there are many thousands of ways in which we use different metals in our bodies.
What I want to concentrate on, this is really the main point of the talk that molecular form matters. If I was to say arsenic to you what would you think of? Poison. That what everybody say. Everyone thinks of poison when they think of arsenic and this is a famous movie and it’s really infamous these are poison since the middle ages. it’s thought to be responsible for numerous deaths of important people including Napoleon Bonaparte, it was possibly used by the Borges’s in poisoning their denigrates , it’s also a leading candidate for infant cock deaths . I can tell you more about that in the end I’m not going to mention it again in the talk about molecules are important. Sometimes arsenic is poisonous but sometimes it isn’t. Here is a cause where it is poisonous. This is lucidity, otherwise known as the Jew of death. it’s a wagers, this is a the fore arm of a marine who was in Iraq in 1991 was exposed to small amounts lucidity that Sad am had at that time in his possession. He rolled up his protective suit and his forearm was exposed and you can see the short exposure to the small amount of Lucite caused all these nasty blisters. Its terrible stuff, its deadly poison if you ingest it will kill you. This is a very toxic arsenic molecule. The arsenic atom is this purple atom right here. The scientist name for is chloral vinyl arsine dye chloride.
There are other molecules such as arsine betain. Arsine betain you get in fish and in all sea food really. You get it in lobster, you get it in shrimp, and you get in in crab. Any kind of seafood that you take you have tot .02% in fish and that’s an awful lot but nobody ever worries about being poisoned by arsenic from eating fish and you shouldn’t worry about it either because it’s nontoxic. This is an example of an arsenic molecule that is not toxic at all. It enters our bodies, circulates in our blood stream and during course it is excreted in the urine it doesn’t harm us it’s not a toxic compound and the difference is in the molecule. The molecule is very important. It’s the same eyelet if anyone is a chemist, they are even the same oxidation state. It’s the different molecule with the same element, different properties. Molecules are very import.
Another example, everyone knows that mercury is one of the most toxic elements its almost common knowledge but not in all its molecular forms. Cinnabar is a good example of relatively nontoxic form of mercury. Here you can see a fragment of the structure, the local structure of cinnabar and you can see the shiny atoms, those are the mercury atoms and the yellow ones are actually sulphur. Cinnabar has been used in jewellery and here’s a pendant made of cinnabar. People have constructed drinking cups of cinnabar and drunk from them regularly and they have suffered no apparent short term effects from this exposure. I wouldn’t recommend drinking from cinnabar cups or wearing cinnabar jewellery but you can contrast it within this substance, dimethyl mercury and a few drops of this on your skin will kill you. It looks just like water, its a little clear liquid and you can see a little bit of it in this vial. Clearly here the difference is in the molecule, molecule matter. It’s very important what the molecule is.
It’s not just the metal that matter it’s also the molecule. What molecule a metal is contained in affects absolutely every aspect of how it will affect us and our environment. Whether it is beneficial, toxic, or the nine. It’s vital to know the molecule form if we are to understand these things. Now I’m going to move on a little bit and say how can slack help. This is a picture of slack sites, many of you especially if you have been to earlier lectures will be familiar with this. This is the 280 freeway, this is the liana and the part of slack I’m going to talk about is this part down here which SSRL, the Stanford Singotorum Radiation Laboratory. I used to work there for 11 years and is still come back there to do experiments. `Herman Winnick gave you a lovely talk on April 27th maybe some of you were here, Singotorum Radiation, the light fantastic and here is the URL where you can find information and actually watch the lecture online if you wish. This is that Stanford Singotrum Radiation laboratory and this can help us understand molecular form. It helps by being a source of what is called Singortrum radiation. This is a very intense beam of x-rays and here you can see this a short movie clip that has been taking of a beam of x-rays passing through air. You can see its emerging from here and there is a little moat of dust being caught in the beam here as it hits the beam stop over here.