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Unless otherwise stated, all images in this file have been reproduced from: Blackman, Bottle, Schmid, Mocerino and Wille, Chemistry , 2007 (John Wiley)      ISBN: 9 78047081 0866 . CHEM1002 [Part 2]. A/Prof Adam Bridgeman (Series 1) Dr Feike Dijkstra (Series 2) Weeks 8 – 13

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slide1

Unless otherwise stated, all images in this file have been reproduced from:

Blackman, Bottle, Schmid, Mocerino and Wille,Chemistry, 2007 (John Wiley)     ISBN: 9 78047081 0866

chem1002 part 2
CHEM1002 [Part 2]

A/Prof Adam Bridgeman (Series 1)

Dr FeikeDijkstra (Series 2)

Weeks 8 – 13

Office Hours: Monday 2-3, Friday 1-2

Room: 543a

e-mail:adam.bridgeman@sydney.edu.au

e-mail:feike.dijkstra@sydney.edu.au

slide3

Summary of Last Lecture

  • Complexes III
  • Transition metal atoms of the first transition series have electron configuration [Ar]4sx3dy where x + y is the group number
  • For the cations, the electronic configuration is [Ar]3dz where z = group number – oxidation number
  • These electrons occupy the ten d-orbitals and, if this leads to unpaired electrons, the complex is paramagnetic
  • Complexes in which the 3dorbitals are not empty, half full or full are coloured due to excitations of the electrons
slide4

Complexes IV

  • Lecture 15
  • Metals in Biological Processes
  • Essential Elements
  • Toxic Elements
  • Medicinal Uses
  • Blackman Chapter 13
  • Lecture 16
  • Chemical Kinetics
  • Rate of Reaction
  • Rate Laws
  • Reaction Order
  • Blackman Chapter 14, Sections 14.1 - 14.3
the biological periodic table

The Biological Periodic Table

essential

medicinal

archaea

toxic

metal ions in biology
Metal ions in biology fall into three groups:

Essential elements e.g.Na+, K+, Mg2+, Ca2+,

Fe2+/3+, Cu+/2+, Zn2+

Toxic elements e.g.Pb2+, Hg2+, Be2+

Elements used in medicine e.g.Li+, Pt2+

Metal Ions in Biology
essential elements na and k
Essential Elements - Na+ and K+
  • Maintaining the Na+ and K+ concentrations requires a pumpingsystem and a lot of energy (ATPase)

Outer membrane

Na+, K+ pump

Inner membrane

(inside of the cell)

iron oxygen transport storage
Iron – Oxygen Transport/Storage
  • Square planar coordination of Fe by porphyrin ligand
  • Oxygen binds reversibly to the free coordination site of Fe
slide10

O2 Transport Complexes

  • In humans, transport system (haemoglobin) and storage system (myoglobin) are both Fe(II) complexes:

myoglobin

haemoglobin

affinity of myoglobin > affinity of haemoglobin

affinity of haemoglobin increases as O2 pressure grows – cooperative effect

muscle

lungs

slide11

Haemoglobin and Myoglobin - Structures

  • Haemoglobin consists of 4 haem groups, myoglobin consists of 1 haem group:

distal histidine residue

proximal histidine residue

slide12

Haemoglobin and Myoglobin - Function

weak H-bond?

enforcedbending

distal histidine residue

distal histidine residue

proximal histidine residue

proximal histidine residue

partial prevention of (irreversible) CO attachment

slide13

Haemoglobin – Cooperative Effect

  • Unoxygenated protein contain Fe(II) d6:
  • Ion has is too large to fit in haemring and actually sits slightly below it
  • Oxygenated protein contains smallerFe(III) d5 which fits into ring
  • The motion of the proximal group is transferred through protein structure to the next deoxygenated haem group decreasing its activation energy for O2 attachment

proximal histidine residue

slide14

Carbonic Anhydrase

  • Zn2+-OH2 is acidic:
    • N3Zn-OH2 N3Zn-OH + H+
  • Metal is bonded to "OH-" which is a good nucleophile
  • Binds CO2 reversibly for transfer from muscles to lungs
    • CO2 + OH- CO32-
trace and toxic elements

Essential Trace Element

Trace and Toxic Elements
  • Lack or shortage of a trace element is damaging to health, as is an excess.
  • Low concentrations of toxic metals may be tolerated but at even moderate concentrations they damage health.
ca 5 po 4 3 oh s
Ca5(PO4)3(OH)(s)

Lead in the Body

  • Pb2+ has approximately the same size and charge as Ca2+ - it can substitute for Ca in biological systems especially bone and teeth.
  • Many poisons act due to have the same size/charge ratio as an essential molecule/ion

PbCa4(PO4)3(OH)(s)

remove as [Pb(EDTA)]2-

slide18

Two mice with solid Sarcoma-180 tumors

Untreated

died day 21

tumor 3 g.

Bottom mouse treated with cis-[PtCl2(NH3)2] on day 8. Tumor completely regressed by day 14. Died of old age 3 years later.

pt anti cancer drugs1
Pt Anti-Cancer Drugs
  • All Pt(II) complexes are square planar
  • trans-diamminedichloroplatinum
  • inactive
  • cis-diamminedichloroplatinum
  • very active
pt anti cancer drugs2
Pt Anti-Cancer Drugs
  • cis-Pt(NH3)2 bonds to two N-bases in the DNA
    • causes DNa helix to "kink" preventing it from replicating
  • trans-Pt(NH3)2 cannot bind to DNA
slide21

Summary: Biological Periodic Table

  • Learning Outcomes - you should now be able to:
  • Identify essential, toxic and medicinal elements
  • Explain functioning of metals in body
  • Relate medicinal uses to function of element
  • Think about consequences for drug design (for example: why cis-PtCl2(NH3)2 is active but trans form is not)
  • Next lecture:
  • Reaction kinetics
slide22

Practice Examples

Hemochromatosis or “iron overload” is a potentially fatal disorder in which excess iron is deposited in the bodily organs as insoluble hydrated iron(III) oxide. It can be treated by administration of desferioxamine B (Desferal), a natural substance isolated from fungi.

Desferal

Desferal is taken over 8-12 hour periods up to six times per week.A value of logK = 30.6 is associated with the following equilibrium:

Fe3+ + LH3+FeL+ + 3H+ where LH3+ = Desferal

Briefly describe the chemical basis for the use of Desferal in iron overload therapy.

slide23

Practice Examples

en = ethylenediamine = NH2CH2CH2NH2