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Chemistry (including Biochemistry)/antacids
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Question
Dear Ms. Robichaud,
These are not homework questions. It’s been 6 decades since I’ve seen the inside of a classroom. Would you happen to know if all forms of oral magnesium are antacid? I scoured the Internet via Google and came up with all kinds of oral mag substances. Magnesium Citrate, Magnesium Hydroxide, Magnesium Oxide, Magnesium Proteinate, Magnesium Glycinate, Magnesium Taurate.
Do you know if all of these neutralize acid? I know some of them are billed as antacids, like Mag Ox. And some are probably more potent antacids than others. Some are mainly used as laxatives, like Mag Citrate. But are all magnesiums (if that is a word) antacids?
Thank you for your time.
Levi
Hi Levi!
I know the beginning of my bio looks harsh; it's to prevent students sending me their entire homework assignments. Believe it or not, it happens anyway, but what more can I do? ;)
On to your question.
What is an antacid? You might remember the concept of pH from school, which relates how many free hydrogen ions are in solution to the pH strength and behavior of that solution. Close to pH 0 you have a strongly acidic solution, while close to 14 you have a strongly basic one. Pure water is neutral at pH 7. Either strong acids or strong bases are caustic and very reactive. The contents of your stomach are usually around pH 2. This helps break down your food into small enough bits that your cells can use them as fuel.
Marketers came up with the term 'antacid' for substances you take to counteract an excess of stomach acid, since not everyone might recognize 'base' as the opposite of 'acid'.
So where does magnesium fit in to this equation, if acids and bases are determined by hydrogen ion concentration? In solution, hydrogen ions wander around as naked protons, 'looking' for two electrons to complete their outer shell. Outer shell? If you don't remember octet theory, this essentially means the hydrogen is looking for a bonding partner who's got two electrons to spare. What's cool about magnesium ions is that they do the same thing: they are looking for two electrons for a bonding partner. It is worth noting that Mg2+ is somewhat less reactive than H+ because it still has some of its electrons, while H+ has none. However, excess double-positive metal ions like this result in a solution that registers as 'acidic' on the pH scale, even if there aren't many hydrogen ions in solution. Chemists call these metal ions 'Lewis Acids', if you'd like to read up some more on this. In antacids they're often salts utilizing sodium, calcium, and aluminum.
A solid metal salt is usually a molecular lattice of positively charged and negatively charged atoms or atom clusters. So magnesium in this case is positively charged, because it is bereft of two negatively charged electrons. For a salt to exist as a solid, this has to be put with something that is negatively charged to render the substance stable on your countertop. So that's why there is such a variety of magnesium salts; the other molecules are the 'stuffing' that permits the magnesium ions to exist in a balanced solid lattice.
Why the extended ramble? Well, for a good magnesium antacid, the partner in the salt must be basic in character, since the magnesium ion is the 'acid' half of the acid-base salt combination. So Magnesium hydroxide would be the best antacid of the bunch, as OH ions are very strongly basic. Magnesium carbonate or bicarbonate would also be a decent antacid. I don't think MgO dissolves easily, so that might not be your best bet. I don't know offhand the pKa (an indicator of the pH 'strength' or 'position') of the other complex ions you listed, and my google searches didn't turn up a convenient table. Most likely that information would be in the CRC handbook of Chemistry and Physics.
My guess would be if you wanted an antacid, stick with carbonate ions or hydroxide ions for the most relief for your salt.
Please feel free to follow-up if you have further questions.
Further reading to explain concepts discussed:
http://en.wikipedia.org/wiki/PH
http://en.wikipedia.org/wiki/Lewis_acids_and_bases
http://en.wikipedia.org/wiki/Ion
http://en.wikipedia.org/wiki/Acid%E2%80%93base_reaction#Acid.E2.80.93alkali_reac
http://en.wikipedia.org/wiki/Octet_rule
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Answers by Expert:
Trista Robichaud, PhD
Expertise
No homework questions, especially ones copied and pasted from textbooks. I will answer questions about principles or give hints, but I do not do other's homework. I'm comfortable answering basic biochemistry, chemistry, and biology questions up to and including an undergraduate level of understanding. This includes molecular biology, protein purification, and genetics. My training/inclination is primarily in structural biology, or how the shapes of things affect their function. Other interests include protein design, protein engineering, enzyme kinetics, and metabolic diseases such as cancer, atherosclerosis, and diabetes. My chemistry weaknesses are that I do not know organic or inorganic synthesis well, nor am I familiar with advanced inorganic reactions. I will attempt quantum mechanics and thermodynamics questions, but primarily as they relate to biological systems. Furthermore, I cannot tell you if a skin photograph is cancerous, or otherwise diagnose any disease. I can tell you how we currently understand the basic science behind a disease state, but I cannot recommend treatment in any way. Please direct such questions to your medical professional.
Experience
I hold a PhD in Biomedical Science from the University of Massachusetts Medical School in Worcester. I specialize in Biochemistry, with a focus on protein chemistry. My thesis work involved the structure and functions of the human glucose transporter 1. (hGLUT1) Currently I am a postdoc working in peptide (mini-protein) design and enzymology at the University of Texas Health Science Center in San Antonio, Texas. I am in Bjorn Steffensen's lab (PhD, DDS), studying gelatinase A and oral carcinoma.
Organizations
2001 American Association for the Advancement of Science
2007 American Chemical Society
2007 Protein Society
2011 UTHSCSA Women’s Faculty Association
Publications
Levine KB, Robichaud TK, Hamill S, Sultzman LA, Carruthers A. Properties of the human erythrocyte glucose transport protein are determined by cellular context. Biochemistry 44(15):5606-16, 2005. (PMID 15823019)
Robichaud TK, Appleyard AN, Herbert RB, Henderson PJ, Carruthers A “Determinants of ligand binding affinity and cooperativity at the GLUT1 endofacial site” Biochemistry 50(15):3137-48, 2011. (PMID 21384913)
Xu X, Mikhailova M, Chen Z, Pal S, Robichaud TK, Lafer EM, Baber S, Steffensen B. “Peptide from the C-terminal domain of tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) inhibits membrane activation of matrix metalloproteinase-2 (MMP-2)” Matrix Biol. 2011 Sep;30(7-8):404-12. (PMID: 21839835)
Robichaud TK, Steffensen B, Fields GB. Exosite interactions impact matrix metalloproteinase collagen specificities. J Biol Chem. 2011 Oct 28;286(43):37535-42 (PMID: 21896477)
Poster Abstracts:
Robichaud TK, Carruthers. A "Mutagenesis of the Human type 1 glucose transporter exit site: A functional study." ACS 234th Meeting, Boston MA. Division of Biological Chemistry, 2007
Robichaud TK, Bhowmick M, Tokmina-Roszyk D, Fields GB “Synthesis and Analysis of MT1-MMP Peptide Inhibitors” Biological Chemistry Division of the Protein Society Meeting, San Diego CA 2010
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Catalytic Domain Exosites Contribute to Determining Matrix Metalloproteinase Triple Helical Collagen Specificities” Dental Science Symposium. UTHSCSA 2011
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Exosite Interactions Determine Matrix Metalloproteinase Specificities” Gordon Research Conference on Matrix Metalloproteinase Biology, Bristol RI 2011
Education/Credentials
Oakland University, Auburn Hills MI BS, Biochemistry 1998
University of Massachusetts Medical School, Worcester MA PhD, Biochemistry & Molecular Pharmacology 2001-2008
University of Texas Health Science Center, San Antonio TX Postdoc, Biochemistry 2009-Present
Awards and Honors
1998 Honors College Graduate, Oakland University
2009 Institutional National Research Service Award, Pathobiology of Occlusive Vascular Disease T32 HL07446
2011 1st Place, Best Postdoctoral Poster, Dental Science Symposium, UTHSCSA, April 2011
Past/Present Clients
Invited Seminars:
Robichaud TK, Fields GB. “Synthesis and Analysis of MTI-MMP Triple Helical Peptide Inhibitors” Pathology Research Conference, University of Texas Health Science Center San Antonio Pathology Department (June 18th, 2010)
Robichaud TK & Hill, B “How To Give A Great Scientific Talk” Invited Lecture, Pathobiology of Occlusive Vascular Disease Seminars, UTHSCSA (Nov 11th 2010), Cardiology Seminar Series, Texas Research Park (Feb 21st, 2011)
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Exosite Interactions Determine Matrix Metalloproteinase Specificities” Gordon-Keenan Research Seminar “Everything You Wanted to Know About Matrix Metalloproteinases But Were Afraid to Ask” Bristol, RI (Aug 6th, 2011)
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