Bulk and trace elements - Kémiai Intézetchem.science.unideb.hu/Pharm/LectureBioInorg.pdf · Bulk...

Bulk and trace elements – bulk elements: C, H, O, N, S, P– maintaining the osmotic pressure body fluids

Na, K, Ca, Mg, Cl

– essential trace elements:F, I, Se, Si, Sn (main group elements)Fe, Zn, Cu, Mn, Mo, Co, V, Ni (transition metals)

– potential trace elements: B, Ti, As, Pb, Cd, W, ....– toxic elements

Average abundance of trace elements(70 kg individual)

0.15100S1.0680P2.61815N9.76780H18.012590C65.145550OOrganic elements%weight (g)element

0.000014 mgMo0.0000312-20 mgMn0.0001480-120 mgCu0.0042-4Zn

0.0074.2-4.6FeTrace elements(<100 mg/body kg)

0.0642Mg0.1070Na0.16115Cl0.36250K2.421700CaBulk elements

Average amount of trace elements (70 kg individual)

Trace elements

1. The abundance of elements in different living organisms is in a given concentration range

2. The decreasing of abundance of elements causes physiological changes (diseases)

3. Administration of missing trace elements improve the physiological conditionThey take part in the metabolism.

4. The elements have defined biochemical functions

Trace elements

µg/day 10 50 Se 200 103 104

mg/day 0,5 2 F 10 20 100

survival deficiency optimal toxicity lethalit

therapeutic width

Roles of trace elements

1. Transport of biological small moleculespl. O2-transport: hemoglobin (Fe), hemocianin (Cu)

O2-storage: mioglobin (Fe)

2. Activation of molecules: metalloenzymes, enzymes activated by metal ionsa) catalysing of redox processes (Fe, Cu, Mn, Co, Mo, Ni)

biological oxidation, reduction of substrateb) catalysing of acid-base processes (Zn)

3. Secunder conformation of macromolecules– determination of conformation of enzymes– determination of conformation of proteins, nucleic acids

4. Metabolism of microelements– uptaking, transport, storage of trace elements

Roles of trace elements

Experimental methods for study of biological systems

− UV-visible (UV) spectroscopy (exited electron →groundstate)− electronspin resonance spectroscopy (ESR) (interaction between unpaired electron and magnetic field)− nuclear magnetic resonance spectroscopy (NMR) − X-ray diffraction (study of solid crystals)− Mössbauer spectroscopy (study of iron-, tin-complexes)− molecule modelling (computational modelling)

Abundance of trace elements in a caveman andtoday (ppm)

1701,70,01Pb> 2000,19<0,001Hg7000,70,001Cd1,00,40,4Ti2,30,90,4Al2,30,70,3B1,00,030,03Co1,00,10,1Mo1,21,21,0Cu1,03333Zn1,06060Fe

ratiotodaycavemanelement

Composition of earth crust and see water (ppm)

5⋅10–70,00355Cu∼10–8∼10–71-100Ln0,010,011,5Mo∼10–60,0005100Cr∼10–70,0014400Ti∼10–53,0277000Si∼10–70,0181300Al14619000130Cl0,371005028300Na

see/earthsee waterearth crustelement

- circumstances of life origin- chemical factors(complex formation ability, solubility, reversibility of bound, hard-soft acid-base properties)

The origin of life

Chemical evolution: formation of simple and more complicate organic molecules from elementsPrebiological evolution: formation of living cells from group of complicate organic compoundsBiological evolution: the development of living world

Coordination chemistry of metal ions

Complex formation proecesses:M(H2O)n + L ML(H2O)n-1 + H2O

MLn-1(H2O) + L MLn + H2O

M(H2O)n + nL MLn + nH2Oβn = K1·K2· ... ·Kn

]L][)OH(M[])OH(ML[K

n2

1n21

−=

]L)][OH(ML[]ML[K

21n

nn

−

=

nn2

nn ]L][)OH(M[

]ML[=β

Complex formation processes

General equilibrium

pM + qA + rB + sH MpAqBrHs

M: metal ion (oxidation number: 1-3 (4)) or oxoanionA, B: ligands

Types of coordination compoundsa/ parent complexes: complex formed with one ligand:

MA, MA2, MA3 .... MAN (N: coordination number)b/ mixed ligand complexes: complex formed with two or more ligands:

M + A + B MAB orMA2 + MB2 2MAB

c/ protonated complexes: the non-coordinated donor groups of ligands are protonated

M + HnA M(AH) + n–1 H+


Types of coordination compoundsd/ deprotonated complexes: M + A M(AH–1) + H+

−deprotonation and coordination of ligands (e.g.: alcoholic group, amide group−deprotonation of coordinated water moleculeMA(H2O)n MA(H2O)n–1(OH) + H+

c/ polynuclear complexes: nM + mA MnAm

(A: bridge ligand or ligand containing more donor atoms)


Reactions of metal complexes 1. Substitution of ligands

MA + B MB + Ain solution:

M(H2O)n + nA MAn + nH2Othermodinamic aspect: stable, instable complexes (lg β)kinetic aspect: labile (fast exchange), inert (slow exchange)Biological importance:

MXY + L MXL + Y(X - polifuntional macromolecule, Y – small molecule)e.g.: Zn-carboxypeptidase, Fe-mioglobin


Reactions of metal complexes2. Redox reactions

ε(oxidated form) < εo < ε(reduced form)

Fe(III)/Fe(II) ε (V) Cu(II)/Cu(I) ε (V)εo H2O +0,77 H2O +0,17

OH– –0,56 glycine –0,16oxalate +0,02CN– +0,22 bipiridine +0,96 pyridine +0,27fenantroline +1,10 imidazole +0,35

CN– +1,10


Factors influenced stability of complexes:• Type and charge of metal ion

- the complex of metal ion with +3 oxidation state is more stable- the stability of complexes of 3d elements with +2 oxidation state follow the Irving-Williams series

Mn(II) < Fe(II) < Co(II) < Ni(II) < Cu(II) > Zn(II)(related to the decrease in ionic radii)


Factors influenced stability of complexes:• Type of metal ions and ligands

- hard metal ions (Lewis-acids) form stable complexes with ligands containing hard donor atoms (F, O) - soft metal ions (Lewis-acids) form stable complexes with ligands containing soft donor atoms (I, S)

• Type of ligands- formation of chelate rings (five- or six-membered ring) →enhance the stability of complexes: chelate effect


Potential donor atoms in biological systems

• Hard-soft acid-base groups of metal ions and ligands

Oxigen containing ligands: H2O, CO3

2–, NO3–, PO4

3–, ROPO3

2–, (RO)2PO3–,

CH3COO–, OH–, RO–, R2O, crownethersNitrogen containing ligands:NH3, N2H4, RNH2,Cl–

H+, Na+, K+

Mg2+, Ca2+, Mn2+, VO2+

Al3+, Co3+, Cr3+, Ga3+, Fe3+, Tl3+, Ln3+, MoO3+

hard bases (ligands)hard acids (metal ions)

,

Sulphur containing ligands:RSH, RS–, R2S, S2O3

2–

R3P, (RS)2PO2–,

(RO)2P(O)S–,RNC, CN–, CO, R–, H–, I–

Cu+, Au+, Tl+, Ag+, Hg22+

Pt2+, Pb2+, Hg2+, Cd2+, Pd2+, Pt4+,

soft bases (ligands)soft acids (metal ions)

Br–, SO32–,

Nitrogen containing ligands:NO2

–, N3–, N2,

Fe2+, Ni2+, Zn2+, Co2+, Cu2+,Pb2+, Sn2+, Ru2+, Au3+

intermediate bases(ligands)

intermediate acids (metal ions)

NH2

NNH

Potential donor atoms in biological systems

The most important ligands in biological systems

• amino acid, peptide, protein• nucleic acid base, nucleoside, nucleotide• porfirins• polyphenols, carbohydrates, glycerides

Metal complexes of amino acids and peptides• -COO–-coordination: Na+, Ca2+, Al3+

• -NH2-coordination: Ag+, Hg2+

• (NH2,COO–) coordination: M2+ (M+, M3+) transition metal ions

amino acid dipeptide

coordination is influenced: • by R1-Rn sidechain• pl: Asp, Glu – carboxylate group,• His – imidazole ring, • Cys – SH-group

Nukleinsavak és alkotórészeik

N

N N

N

O CH2 O P

O

-O

O P

O

O-

O P

O

O-

O-

NH2

HO OH

nukleobázis: N-donorok soft fémek

foszfát: O-donor hard fémek

Nucleic acids and their components

nucleic base: N-donors

phosphate: O-donors

soft metal ions

hard metal ions

N

N N

N

MM2+ + H2P MP + 2 H+

Order of stabilitiesMg(II) < Zn(II) < Cu(II) < Fe(II) < Ni(II) < Pd(II) < Pt(II)

N = 4 (Ni(II), Pt(II), Pd(II)) – all coordination sites are occupiedN = 6 (Fe(II), Co(II), Mg(II), Zn(II)) – axial coordination site

Metalloporphyrines

Complexes of alkali metal ions

No stable complexes with “normal” ligands

Crown ethers: macrocyclic polyethers

18-crown-6 Dibenzo-crown-6

OO

O

OO

O OO

O

OO

O

cryptand e.g. 2,2,2 NO O

NO OO O

Li+ complex of 12-crown-4

Complexes of alkali metal ions

Factors influencing the stability of alkali complexes

O

O O

O

OO

O

OO

O

a) the size of cavity

K+> Rb+> Cs+ > Na+> Li+

lgβNa(I) = 2.2 (methanol)lgβK(I) = 1.3 (methanol)


NO O

NO OO O

( )m( )n

( )n(vízben) lgβLi(I) lgβNa(I) lgβK(I)

m=0, n=1 5,3 2,8 <2,0

m=1, n=0 2,5 5,4 3,9

m=n=1 <2,0 3,9 5,4

m=1, n=2 <2,0 1,65 2,2

m=2, n=1 <2,0 <2,0 <2,0

m=n=2 <2,0 <2,0 <2,0

a) the size of cavity

Factors influenced the stability of alkali complexes

c) number of binding side

lgβNa(I)=6,95 lgβK(I)=9,45

NO O

NO OO O N

O ON

O O

lgβNa(I)=3,0 lgβK(I)=4,35


methanol/water = 95/5

d) type of binding side

OO

O

OO

O

ON

O

ON

O

CH3

CH3




d) type of binding side

NO O

NO OO O N

N NN

O OO

CH3 CH3

O


lgβNa(I) = 3.9 (water)lgβK(I) = 5.4 (water)

lgβNa(I) = 2.5 (water)lgβK(I) = 2.6 (water)

Selectivity of ligands

NO O

NO OO O

Importance• specific chelators (diagnostic, therapy)• phasetransfer: transport of KMnO4 in organic phase

Complexes of alkali earth metals

O-donor ligands are preferred• crown ethers, macrocyclic• edta

NCOOH

COOHHOOC

HOOCCH2CH2N

ON

O

O

N O

O

O

O

O

Alkali and alkali earth metal ions:biological roles

Abundance in human body• cca 1 % of body (trace elements < 0,01 %)• e.g. 170 g potassium/ 70 kg, 1000-1250 g Ca, 26 g Mg

• bulk elements: C, H, O, N, S, PNa, K, Ca, Mg, Cl

Distribution (mmol/1000 g)

22.0440.0Extracellular fluid of neuron

410.049.0Intracellular fluid of neuronCalamary

2.51.55.0152.0blood plasma0.12.592.011.0blood cell

Ca2+Mg2+K+Na+


Membrantransportprocesses


Membrantransport processesTransport across the membrane

Diffusion: non-selective, in direction of concentrationgradient

Facilated passive transport: by means of carriers (ionophors)energy is not required

Active transport: in opposite direction of contentrationgradient, energy is requiredenergy source: hydrolysis of ATP


Membrantransport processesPassiv transportLigands: carrier ionophors: e.g. Valinomicin


Chanel ionophorse.g. Gramicidin A

Biological rolesNa+, K+:• maintaining of osmotic pressure of cells• take part in acid-base processes• regulation of membrane potentials• K+: take part in determination of conformation of biomolecules, in activation of enzymes, in synthesis of acetilcoline• Na+: take part in activation of enzymes, in secondary active transport


Biological roles of alkali metals

Na+, K+: regulation of membrane potentials

Na+, K+: regulation of membrane potentials

Biological roles of alkali metals

Ca2+:• regulation the processes of nerve transmission• regulation the muscle contraction• regulation electrolyte balance• blood coagulation• building up bones and theeths

Biological roles of alkali earth metals

Ca2+: regulation the processes of nerve transmission


P1

ADP

Ca2+: muscle contraction

Ca2+-binding proteins• trigger proteins: e.g.: calmodulin

Buffer proteins: pl. calbindin• Ca-storage proteins: calreticulin, calsequestrin• blood coagulation: prothrombin• building up bones: osteocalcin: Ca5(PO4)3OH

Ca2+-binding proteins: blood coagulation - protrombin


Mg2+:• activation of enzymes, determination of conformation of proteins• take part in hydrolysis of ATP, universal source of energy → metabolism of energy • building up of bones• part of chlorophyll (photosynthesis)


Mg2+ - photosynthesis

6 CO2 + 6 H2O = C6H12O6 + 6 O2

Two photosystemI. reduction of CO2 (dark reaction)CO2 + NADPH + H+ + ATP → C6H12O6

+ ADP + Pi + NADP+

II. photolysis of water (light reaction)H2O + NADP+ + Pi + ADP

O2 + NADPH + H+ + ATP⎯⎯→⎯light

chlorophyll



90Sr – radioactive, t½ = 28 year, can be built up in bonesBaSO4 – contrast compound (X-ray)


Complexes of iron(II)

Complexes:• in solution: [Fe(H2O)6]2+ (octahedral, pale green)• easy oxidation to iron(III) (in basic solution)• redoxpotential of Fe(III)/Fe(II) is changed by formation of complexesFe3+/Fe2+ : CN– +0,36 V

H2O +0,77 VPhen +1,12 V

Complexes:• intermediate (hard/soft) acid: binding to O-, N- and S-donor-atoms

• most important ligands: aromatic nitrogen donors in chelatable position• bipiridine, fenantroline, porphyrins

• usually octahedral complexes (some tetrahedral complexes)

Complexes of iron(II)

Complexes:• in solution: [Fe(H2O)6]3+ (pale violet)• stable complexes in acid and basic pH range• characteristic reaction: hydrolysis

pH > 1: [Fe(H2O)6]3+ + H2O [Fe(H2O)5(OH)]2+ + H3O+

Ks = 1,8⋅10–3

• Dimerization → structure with oxo bridges (yellow)[(H2O)5Fe–O–Fe(H2O)5]4+

Complexes of iron(III)

Complexes:pH > 2: polynuclear structures, mixed hydroxo complexes →Fe(OH)3 precipitation

• usually octahedral complexes• hard acid: • binding to F– and O-donors containing ligands• [Fe(SCN)4]– + 6 F– [FeF6]3– + 4 SCN–

intensive red colorless

Complexes of iron(III)

Biological role of iron

Iron proteins

Hem proteins Non-hem proteins~ 70 % ~ 30 %

iron-sulphur othersproteins

• Human body: cca. 4 g iron (~3 g in hemoglobin)• uptaking of iron: 1 mg/day

Iron proteins

Hem proteins Non-hem proteinsoxygen transport, storage

hemoglobin hemerythrinmyoglobin

electron transfercytochromes iron-sulphur proteins

oxidases, oxygenasescytochrome c oxidase

iron transport transferriniron storage ferritin

Biological role of iron

Globin: contains153 amino acidsHem: Fe-porphyrin

Hem is bound to globin protein via iron ion (without covalent bound)

5. coordination side:imidazole N

Myoglobin (oxygen storage)

Hemoglobin (oxygen transport)

It contains 4 globin units

Fe(II) + O2: iron ion passes to porphyrin ring

uptaking of oxygen: high partial pressure of oxygengiving down of oxygen: low partial pressure of oxygenCO2 + H2O HCO3

– + H+

Hemoglobin (oxygen transport)

parital pressure of oxygen in the lungs

partial pressure of oxygen in the muscle

– oxygen transporter in molluscs

– 4 part, one part contain two iron, it binds one O2

Hemerythrin

• transfer electrons (redox proteins and enzymes)• insert oxygen atoms or dioxygen into organic substrates or catalyse other important organic reaction• coordination number: 5 or 6• interaction between protein and hem moiety: covalent or van der Waals bound

Cytochromes

Cytochrome C

provide electrons via following reaction:

Fe2+ Fe3+ + e–

Cytochrome P450• part of monooxygenase enzymes • activation of dioxygen molecule

RH + O2 + 2 e– + 2 H+ → ROH + H2O

• 5. coordination side: cysteine S • 6. coordination side: H2O

Cytochromes

Cytochrome P450

Catalase– catalysing the disproportion of H2O2

2 H2O2 → 2 H2O + O2

– it contains four same units– 5. coordination side: tyrosine O–

– mechanism:

Fe(III)

O-(Tyr)

Fe(IV)

O-(Tyr)

H2O2 H2O

H2O2H2O + O2

Catalase

• Tetrahedral geometry of iron• Iron binding to inorganic and organic sulphur donors (Cys) S• one e–-pass

• reduced ferredoxin oxidized ferredoxin • unusually low redox potenctial: –0,05 - –0,49 V → they behave as a reduction agents

Iron-sulphur proteins

• rubredoxin: [1Fe]3+(RS–)4 (–0,06 V)• ferredoxins: [2Fe-2S]2+(RS–)4 (–0,3 - –0,4 V)

[4Fe-4S]2+(RS–)4 (–0,4 V)HIPIP: [4Fe-4S]2+(RS–)4 (0,35 V)

– e–

+ e–

Iron-sulphur protein (HIPIP)

Iron-sulphur proteins

Transferrin:Transport: iron(III) form, at neutral pHStructure: M ~ 80.000, 0,15 % irontwo structural units:

one unit: 2 iron(III) + protein

Transport of iron

Siderophores:iron transporter in microorganisms

C

N

R

R

O

O-

Fe+3

3

O-

O-

Fe+3

3

Rhydroxamate-type

e.g. ferrichromcatecholate-type

e.g. enterobactin

Transport of iron

FerritinIt contains 24 protein units (~ 175 amino acids/unit)4500 iron atoms/ferritin (25 %)iron micelle (7 nm diameter) : (FeOOH)8⋅FeO⋅H2PO4

uptaking: iron(II) form, it is followed by oxidation to iron(III)Hemosiderinstorage of excess of ironcca. 45 % iron

Storage of iron

Biological role of copper

• Essential for every living organisms• 80-120 mg / 70 kg body• uptaking: 1,5-3,0 mg/day, < 10 mg• toxicity: > 15 mg• diseases caused by copper:

excess of copper: Wilson diseasemissing of copper: Menke’s disease

Functions of copper proteins

• Oxygen transport, storage: hemocyanin (mollusc)

• Catalysing of redox processesoxidases (blue-copper oxydase), oxygenases, superoxide dismutase

• Copper transport, storage: ceruloplasmin, metallothionein


Superoxide dismutase (SOD)2 O2

– + 2 H+ H2O2 + O2⎯⎯→⎯SOD

His 61

His 78

His 69

H2O

Zn2+

Cu2+

His 44

His 46His 118

Asp 81


Superoxide dismutase (SOD)Zn: regulation of structureCu: takes part in redox processes

Reactions:Cu2+(His–)Zn2+ + O2

– + H+ → Cu+ + (HisH)Zn2+ + O2

Cu+ + O2– + H+ + (HisH)Zn2+ → Cu2+(His–)Zn2+ + H2O2


Ceruplasmine:1005 amino acid (single protein chain), 6 copper

Function: • oxidase• ferrioxidase: Fe2+ → Fe3+

• transport of copper• metabolism of copper → missing of ceruloplasmine →Wilson disease, Menke’s disease


Zinc metalloproteins1940 – first zinc enzyme: carbonic anhydrase1985 – 100 zinc containing enzymes1995 – 300 enzymes + > 100 zinc containing proteins

Role of zinc: • active centrum (catalysing of acid-base processes)• regulating of structure

The second most abundant trace element The least toxic elementEssential for every living organism2-4 g zinc / 70 kg body

Biological role of zinc

Carboanhydrase

• Process:CO2 + H2O HCO3

– + H+

k = 3·10–2 s–1, with enzyme: k = 6·105 s–1

• Zn: tetrahedral geometry, • coordination: 3 histidine + 1 H2O• Zn – H2O → Zn-OH– → interact with CO2

Carboxypeptidase A• Process: hydrolysis of peptide bound at C-termini • 1 Zn + 307 amino acids (M ~ 34.000) • coordination: 2 histidine + 1 glutamate COO– + 1 H2O

Glu 117

His 119

Thr 199

His 96

His 94

His 64

Glu 106

H2O

Gln 92

Zn2+

Carboanhydrase

Carboxypeptidase A

Zinc fingers

• Metalloproteins, which take part in the DNA transcription• Zn: regulation of structure• 9-10 zinc ions, • Zn2+: tetrahedral geometry (His N, Cys S) →the conformation is similar to a finger

Zinc fingers

Pharmaceutical application of metals

Administration of trace elements• treatment of deficiency diaseses Remove of toxic elements• treatment of toxicity of heavy metals

Important aspects:• metal complexes of chelatable or macrocyclic ligands have high stability• neither ligands nor complex are not toxic• ligand is selective

Metal complexes in therapy

Anticancer pharmaceuticals, medicines:cisplatin complexes

cisplatin carboplatin


H3NPt

H3N

Cl

Cl

H3NPt

H3N

O

O

C

C

O

O

Mechanism of cisplatin


H3N (II)Pt

H3N

Cl

Cl

H3N (II)Pt

H3N

Cl

OH2

NH3

Pt(II)H3N Guanin (DNA)

Cl

H3N (II)Pt

H3N

G

G

hydrolysis

DNA

Metal complexes in therapyLithium: maniac depression: Li2CO3

Vanadium: insulin mimic (oral) pharmaceuticals

bis(picolinato)oxovanadium(IV) bis(maltolato)oxovanadium(IV)

OV

N

N

OO

O O OV

O

O

O

OO

O

CH3

CH3


Metal complexes in therapy• Bismuth: gastric ulcer: Bi(NO3)3

• zinc: treatment of ulcers


Metal complexes in therapy• gold: rheumatoid arthritis


+Na-O

S

O-Na+

O

OAu

n

O

H

HO

H

HO

H

HOHH

S

OH

Au

Au S CH2

HC

H2C SO3Na

OH

nMyochrysine

Solganol

Allochrysine

Metal complexes in therapysilver: treatment of infection


SHN

N

N

H2N

O O

sulfadiazin

Contrast compounds• X-ray contrast:

heavy metal salts: e.g.: BaSO4

organic iodine compounds• NMR tomography: Gd-polycarboxylate complexes


Contrast compounds• NMR tomography: Gd-polycarboxylate complexes

NN

N

COO-

-OOC

-OOC

COO-

COO-

N N

NNCOO-

COO-

-OOC

-OOC

DTPA - Magnevist

DOTA - Dotaterm


Radioactive isotopesDiagnosis• > 80 %, 99mTc, γ-ray (t1/2(γ) = 6 hours, t1/2(β) = 212000 years)

Therapy• outer ray source• Injection: 186Re, 188Re


Bulk and trace elements - Kémiai Intézetchem.science.unideb.hu/Pharm/LectureBioInorg.pdf · Bulk...

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