Essential and Trace Elements

• Transition elements

  Elements in groups 3-12 of the periodic table
• The IUPAC defines transition metals as elements with an incomplete d subshell or elements that can form a cation with an incomplete d subshell
• Zinc (Zn), cadmium (Cd) and mercury (Hg) are not typically classified as transition metals
• Metal-based drugs


  • Exhibit unique properties that allow metal ions to interact with biomolecules in a unique way
  • Allow scientists to safely administer even toxic metal ions to the human body
• Coordination and redox behaviour, magnetic moments and radioactivity


  Main unique properties displayed by metal centres
• Transition metals are able to coordinate to electron-rich biomolecules such as DNA, leading to deformation of DNA and cell death
• Transition metals are under scrutiny as potential anticancer agents
• Essential and trace elements


  Traces of certain metals that function as cations and are essential for all forms of life
• Heavy metals such as copper, iron, manganese and zinc are essential for maintaining certain oxidation-reduction equilibria and serve as co-factors for certain enzymes
• Inorganic elements cannot be converted or decomposed to other substances by metabolic processes taking place in the body
• Fourteen essential inorganic elements

  • Iron
  • Copper
  • Zinc
  • Manganese
  • Cobalt
  • Molybdenum
  • Vanadium
  • Selenium
  • Chromium
  • Nickel
  • Tin
  • Iodine
  • Fluorine
  • Silicon
• These essential and trace elements are required in a few micrograms to a few milligrams per day
• These elements play an important role in the biological redox processes and are integral components of enzymes
• Trace elements


  Elements found in the body in mg/kg concentrations
• Ultra-trace elements

  Elements found in the body in concentrations of µg/kg or less
• Deficiency of trace elements can occur due to decreased intake, decreased absorption, chronic loss, or chronic disease of liver and kidney
• Excess concentrations of essential and trace elements may be toxic
• Essential and trace mineral supplements are available orally in their salt form, as oral colloidal mineral solutions or from plant sources to enable better absorption and bioavailability
• Iron


  Silver in appearance, melts at 1528°C, becomes magnetic when an electric current is passed through it
• Iron readily combines with oxygen, the halogens, and nitrogen
• Iron oxidation states


  Most stable is +3 (iron (III)), +2 is reducing (iron (II)), +6 is extremely oxidizing
• In the body, iron is essentially stored as particles of iron (III) hydroxide known as ferritin, surrounded by a protein coat
• In higher animals, iron (III) is carried through the blood stream by proteins called transferrins
• Heme proteins


  Proteins that contain one or more heme groups (iron-porphyrin complex) at their core

  
• Heme proteins


  • Cytochromes
  • Hemoglobin
  • Myoglobin

  
• Cytochromes display a range of redox potentials to meet the specific needs of electron transfer schemes in photosynthesis or respiration
• Cyanide ions bind very tightly to iron in cytochromes, blocking the redox chain and causing toxicity
• Hemoglobin


  Transports oxygen from its source to the site of use within muscle cells
• Oxygen, water, carbon monoxide, and nitrous oxide can all act as ligands to the iron in hemoglobin and myoglobin
• Carbon monoxide binds 50 times more tightly than oxygen to myoglobin and 200 times more tightly to hemoglobin, which can prove fatal with prolonged exposure
• Before oxygen binding, the coordinated iron in hemoglobin and myoglobin lies slightly above the plane of the porphyrin ring, dropping into the plane when oxygen binds

  
• Iodine


  An essential trace element in the human body
• Thyroid hormones thyroxine (T4) and triiodothyronine (T3) contain four and three atoms of iodine per molecule, respectively
• The thyroid actively absorbs elemental iodine from the blood to make and release these hormones, regulated by thyroid-stimulating hormone (TSH) from the pituitary
• Thyroid hormones play a basic role in biology, acting on mitochondria to regulate metabolism
• Iodine deficiency leads to goiter and is the leading cause of preventable mental retardation
• The recommended daily intake of iodine is 150 micrograms for both men and women
• Natural sources of iodine include seaweed and seafood
• Toxicity of iodine


  • Elemental iodine (I2) can cause lesions on skin and is very irritating to eyes and mucous membranes
  • Ingestion of 2-3 grams of elemental iodine is fatal for humans
  • Excess iodide ions in the body can produce symptoms similar to iodine deficiency
• Exposure to radioactive iodine (radioiodine) raises the chances of thyroid cancer, but taking regular iodine can saturate the thyroid and prevent uptake of radioiodine