Introduction to Bioinorganic Chemistry Flashcards
What happens to atomic radius down the group + across the period?
Increases
What happens to ionisation energy down groups 1 + 2 and across period 1?
Increases
What is the equation for ionisation energy?
A(g) —-> A+(g) + e-(g)
What is the equation for e- affinity?
A+(g) + e-(g) —-> A-(g)
Where are elements that have highest e- affinity?
Top right
What is electronegativity?
Ability of an atom within a compound to attract e- towards itself
Where are atoms that are the most electronegative?
Top right
What are hardest atoms?
Highest ionisation energies
= small atoms, near fluorine
What are softest atoms?
Low ionisation energy
What are hard acid and bases?
Less polarisable
Form bonds with more ionic character
What are catalytic metals?
Many enzymes have metals attached to active site to act as catalyst
What factors influence the role of metal?
Valency
Ionic radius
Polarizability
Hydration energy
Radius of hydrated ion
What do hard acids prefer?
Works vice versa with soft acids
Hard bases
What is linear?
sp
What is equilateral triangle?
sp2
What is tetrahedron?
sp3
What is triagonal bi-pyramidal?
sp3d
What is octahedron?
sp3d2
What do different metals prefer?
Different coordination numbers
What are the most common coordination numbers found in biological systems?
4 = square planar tetrahedral
6 = octahedral
What can a ligand be?
Monodentate OR polydentate
What is monodentate?
Only one point of attachment to metal
What is polydentate?
More than one point of attachment too metal
What is ciprofloxacin?
Hard Lewis acid
What is a macrocyclic molecule?
Cyclic molecule (at least 9 atoms), containing 3 donor atoms - typically N, O, S or P
What are macrocyclic complexes?
More thermodynamically + kinetically stable than non-cyclic ligands
Are polydentate ligands more stable than monodentate?
YES
What is the increasing stability of mono, poly + macrocyclic known as?
Chelate effect
What is clinical significance of chelation?
Chelation changes physical + chemical characteristics of both components
What are tetracyclines?
Broad-spectrum antibiotics
Treat the clap
Describe tetracyclines mode of action
Bacteriostatic agents
Target 30s subunit
Block binding of aminoacyl tRNA in A-site
Which metal is involved in mode of action of tetracyclines?
Mg2+
What do tetracyclines form?
Chelates with Ca2+, Mg2+, Al3+, Fe2+ + Zn2+
What chelates do tetracyclines form with M3+?
3:1 drug-metal chelates
What chelates do tetracyclines form with M2+?
2:1 drug-metal chelates
What do Al or Mg hydroxide-based antacids do?
Reduce absorption of tetracyclines
What are tetracyclines not recommended for?
Ca2+ chelates
Kids under 12 = teeth yellow
Pregnant women = effect on skeletal growth
What can metal ions do and what does this mean?
Stabilise conjugate bases
= pKa value of parent acid lowered
What does it mean if an acid has a lower pKa?
STRONGER
What does it mean if a base has a higher pKa?
STRONGER
pKa = pH
50% ionised
What do all carbonic anhydrase inhibitors contain?
All share sulphonamide = WAs
What is carbonic anhydrase involved in?
Regulation of acid/base balance
Production of bicarbonate rich aq humor secretion
What does carbonic anhydrase do?
Catalyse reaction between H2O + CO2 to for carbonic acid
What is the equation for reaction between H2O + CO2?
CO2 (g) + H2O ⇌ carbonic acid ⇌ hydrogencarbonate (bicarbonate) + H+
Which metal does carbonic anhydrase contain?
Zn2+
Why is Zn2+ (metals) so important?
Metal drives it = remove Zn2+ = process doesn’t work
= catalyses process by modulating pKa of H2O = form OH- + giving correct geometry for cleft
Where does Zn2+ sit in carbonic anhydrase?
Bottom cleft, which has 2 faces
What is the hydrophobic face important for?
Carbonic anhydrase
Binding the substrate
What is the hydrophilic face important for?
Carbonic anhydrase
Shuttling proton
Does Ca2+ have a gradient?
YES
= through different cellular compartments
What is the coordination number for Mg2+?
6
What is the coordination number for Ca2+?
7
What can Mg2+ + Ca2+ both be thought of as?
Lewis acids
What is Mg2+ main role?
Catalytic sites of DNA polymerase
What do protein kinases do?
Add phosphate group
What do phosphatases do?
Remove phosphate group
What is the phosphate supplied as?
Mg-ATP
DOESN’T work without Mg2+
How is RNA different to DNA?
Perform catalytic functions
What does tRNA contain?
Half-crucifixes
Mg2+ hold this shape
What do ribosomes require?
Mg2+ ions to catalyse their splicing reactions
Why is Mg2+ important in muscle cells?
Carries ATP/ADP so has to be present for it to be delivered
What does Ca2+ regularly do?
Exchange H2O with other ligands
What is calmodulin?
Protein involved in mediation of Ca2+ signal
Describe structure of calmodulin
Small, acidic protein
Dumbbell shape
Binds 4x Ca2+
What are the major donor groups for Ca2+?
Carbonyl + carboxylate groups