Far be it from me to quibble with an AI, but…while it is certainly possible that a heme prep is contaminated with other metals, things like lead aren’t going to combine with a porphyrin to form a heme-like structure.
Metals much heavier than iron are too large to sit in the plane of the porphyin. So while it is indeed possible to make porphyrin complexes with heavier metals, those metals tend to sit above the plane of the porphyrin (forming an open-face sandwich); or sometimes a second porphyrin is recruited to form a proper sandwich. The map doesn’t look consistent with either of these scenarios. Pat ps It’s lunchtime here, and now I find myself contemplating a lead sandwich… ————————————----------------------------------------------- Patrick J. Loll, Ph. D. (he, him, his) Professor of Biochemistry & Molecular Biology Drexel University College of Medicine Room 10-102 New College Building 245 N. 15th St., Mailstop 497 Philadelphia, PA 19102 USA (215) 762-7706 [email protected] [email protected] > >> On Sep 5, 2025, at 11:23 AM, Oganesyan, Vaheh >> <[email protected]> wrote: >> >> One more less probable cause: could the haem be contaminated with metals >> heavier than Fe? >> I’ve asked that question to Gemini. Below is the response: >> Yes, a haem preparation can be contaminated with metals heavier than iron, >> including toxic heavy metals like lead (Pb), mercury (Hg), cadmium (Cd), and >> arsenic (As). This is a serious concern because these metals can interfere >> with normal heme synthesis and cause a range of health issues. >> Mechanisms of contamination >> Several pathways can lead to haem preparation contamination with heavy >> metals: >> • Environmental pollution and bioaccumulation: Heavy metals from >> industrial activity, mining, and waste disposal are persistent in the >> environment. These metals bioaccumulate in the food chain and can end up in >> the biological tissues from which haem is extracted. >> • Competition with iron in the body: The heavy metals that contaminate >> biological samples can interfere with the final step of heme biosynthesis, >> where iron is normally inserted into the protoporphyrin ring. Lead, for >> example, is known to inhibit the enzyme ferrochelatase, disrupting the >> process. >> • Experimental reagents: Contaminated reagents or laboratory equipment >> used during the haem preparation and purification process can introduce >> heavy metals. Even analytical methods, such as those that involve acid >> digestion, must be carefully controlled to prevent external contamination >> during analysis. >> Vaheh > Patrick Loll [email protected] ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
