SEMMELWEIS UNIVERSITY
Dept. of Biophysics and Radiation Biology,
Laboratory of Nanochemistry
Water, polymers,
macromolecules and biopolymers
Miklós Zrínyi
[email protected]
A peculiar liquid: water
According to Thales water is the primal element or substance from
which all things arose and of which they consist. Water is the the
first principle of all things.
The chemical compositon of water was determined by
Henry Cavendish in 1783.
H 2O
It is essential for all life on Earth
Naturally occurring water is almost completely composed of the
neutron-less hydrogen isotope proton.
Only 155 ppm include deuterium (D), a hydrogen isotope with one
neutron, and fewer than 20 parts per quintillion include tritium (T),
which has two neutrons.
Heavy water (D2O) is water with deuterium content, up to 100%.
It is used in the nuclear reactor industry to moderate (slow down)
neutrons.
In its pure form, it has a density about 11% greater than water, but
otherwise, is physically and chemically similar. (not radioactive)
Water is the only common substance found in all three phases in
nature.
Water exists in liquid, solid, and gaseous states.
71% of earth surface is covered by water (mainly salt water).
70% of fresh water is stored in form of snow and ice.
Water is the basic component of all living
organism.
Water content of Jelly fish 98%,
three month old embryo 94%,
a new born child 72%,
adult 50-60%.
Age dependent water content of a body: 45m% - 75m% (65m%)
Daily excretion :
2500 ml
Daily consumption:
2500 ml
urine 1500 ml
drinks 1600 ml
food 700 ml
200 ml
defecation 200 ml
evaporation 400 ml
perspiration 100 ml
During aging the amount of water in body
decreases.
Water content of different parts of body
M body = 70kg
Vwater = 42l
H 2O
ice
water
steam
°
0,958 A
The molar volume of water at 4 C˚
is minimal, accordingly the density
is maximal.
p [Pa]
p [Pa]
C
The molar volume of most substances in solid state is smaller than in
liquid state. Exception: water
C
A
A
22,1 106
7,4 106
water
ice
O
520 103
O
610
liquid
solid
P
101,5 103
vapour
steam
101,5 103
B
ice
B
0
100
374
-78
-56,4
31,1
T [0C]
Phase diagram of water and carbon-dioxid
T [0C]
H-bonds
water
Hydrogen bond
Basic intermolecular interactions
- ion – permanent dipole
- ion – induced dipole
- permanent dipole – permanent dipole
- permanent dipole – induced dipole
- induced dipole – induced dipole
- H-bond
- hidrofób kölcsönhatás
van der Waals
EH = 4 − 40kJ / mol
Hydrogen bonds are very common in biological macromolecules
During melting the molar volume of water decreases by 8%.
An increase of pressure promotes melting
If the water behaved like any other liquids
- we would not have mountain springs,
- the ice would sediment in water,
- the rivers would be completely frozen,
- we could not skate.
- …..
ice
water
Heat capacity of water
Q = C (T ) mΔT
Heat of evaporation of water
Due to its extensive hydrogen bonds, water has a very high
heat capacity.
Sweating is an effective way to regulate body temperature
Large amount of heat is needed to raise the temperature of
aqueous solution.
Important to regulate the heat generated by metabolic
processes.
jég
Qvap = 2.3 ⋅103 kJ / kg
Qmolar = 41 kJ / mol
Water can store more energy in unit volume that any other liquid.
water
EH = 4 − 40kJ / mol
The ability of water to absorb a lot of heat with little
temperature increase is greatly influences the earth’s climate.
The specific heat capacity of water at room temperature: 4.18 J/gK
The specific heat capacity of steam at 100 C temperature: 2.08 J/gK
High surface tension
Strong wetting due to hydrophilic interaction
(capillary rise)
It does not wet hydrophobic surfaces
(e.g. teflon)
γ = 72, 7 mN / m at 25 C°
Strong intermolecular interactions due to H-bonds gives water a
high surface tension.
Good solvent
Due to its loose structure water dissolves
several gases
. )
( O2 , CO2 ,...
jég
Good miscibility with several components
( CH 3CH 2OH )
Patented by Mengyelejev
Figure 3.7
Good solvent for ions
Good solvent for salts
Na+
−
+
−
−
Na+
+
Cl−
−
+
−
Strong attraction between ions
of different charge?
+
+
−
Cl− +
+
−
Coulombic law
−
−
U elstat =
1
qi ⋅ q j
4πε o
rij
ε o is the electric permittivity of vacuum:ε o = 8.85 ⋅10−12 C 2 N −1m −2
+
−
−
What about the Coulombic law?
Let us express the charge in terms of elementary charges, instead of
Coulomb:
Um =
qi ⋅ q j
rij
⋅1391 kJ / mol
Example:
qi = 1( + ) and q j = 1(−) then U m = −347.81 kJ / mol in vacuum!
Thermal energy at room temperature k BT = 2.5 kJ / mol
What is the role of water?
Water has one of the highest dielectric constant of all liquids.
Excellent solvent for ionic compounds
hydratation
U elstat =
1
qi ⋅ q j
4πε oε rel
rij
The dielectric constant is a scale factor that reduces the magnitude
of electrostatic energy . It weakens the interactions between
charges.
The dielectric constant of bulk water is 78.54 at 25 C°.
The dipole momentum is 1.82 D.
Figure 3.10
pH Scale
0
H+
H+
− H+
H+ OH
+
OH− H H+
H+ H+
−
Acidic
solution
2 H2O
Hydronium
++
H (H
ion
3O3O )
hidroxonium
ion
10−7 mol / dm3
K v = 10−14
pH
1
Battery acid
2
Gastric juice, lemon juice
3
Vinegar, wine,
cola
4
Tomato juice
Beer
Black coffee
5
6
Hydroxide
−
ion OH
(OH−)
OH−
OH−
H+ H+ OH−
−
OH− OH +
H+ H+ H
hidroxide
ion
10−7 mol / dm3
pH = − log ⎡⎣ H ⎤⎦
+
Neutral
solution
OH−
OH−
OH− H+ OH−
−
OH− OH
−
H+ OH
Basic
solution
Neutral
[H+] = [OH−]
7
8
Increasingly Basic
[H+] < [OH−]
+
Increasingly Acidic
[H+] > [OH−]
Autoprotolysis
Rainwater
Urine
Saliva
Pure water
Human blood, tears
Seawater
Inside of small intestine
9
10
Milk of magnesia
11
Household ammonia
12
13
Household
bleach
Oven cleaner
14
Macromolecules
Hydrophobic interactions
Hydrophobic interaction describes the influences that
causes nonpolar substances to cluster together to
minimize their contact with water.
ΔG = ΔH − T ΔS
Aggregates or giant molecules?
W. Kauzman
Hermann Staudinger (1881- 1962)
The Nobel Prize in Chemistry 1953
Basis for many important chemical and biological phenomena
ΔH > 0
ΔS > 0
ΔG < 0
As a result of hydrophobic interactions the nonpolar molecules
come together , releasing some of the ordered water molecules in
the clathrate structure, thus increasing entropy.
Bond energy and stability
Organic and inorganic polymers
Bond energy; kJ/mol
bond
Energy
kJ/mol
C-C
345
C-O
350
C-N
290
C-P
265
Si-Si
230
Higher bond energy
More stable compound
polysilane
explosive!
Bond
Energy
kJ/mol
C-C
345
SiH 4
Si-H
395
Si5 H12 explosive
Si-Si
226
Bond
Energy
kJ/mol
C-C
345
Si-O
370
Bond
Energy
kJ/mol
C-O
350
C-N
290
P-O
350
Monomers
H2C
Propylene
CH3
CH3
Isobutylene
H2C
CH3
O
H2C
OH
O
H2C
O
CH3
Acrylic acid
Methacrylate
CH3
O
H 3C
Vinylacetate
O
CH 2
H2C
H2C
O
CH3
CH2
Vinylmethylether
Butadiene
CH3
H2C
CH2
Polymers and macromolecules are giant molecules!
stable
Isoprene
synthetic
biopolymers
PDMS
monomer unit
Number of monomer units: N
RNA
The longest macromolecule DNA :
several meter!
Monomer units
Monomers
DNA
109 < N < 1010
Monomer units
Homopolymer
A A A A A A A A A A A A
Monomer units
Copolymer nomenclature
A A A B B B A A A B B B
blocky
A B A B A B A B A B A B
alternatig
A A B B A B B A A B A B
statistical
A A A C A A A A C A A A
B
B
B
B
B
B
grafted
Copolymer examples
Synthetic polymers
Biopolymers
DNA:
four different
monomer units
proteins:
20 different amino
acid units
Polyelectrolytes
Anionic
Cationic
Macromolecules with branching
Cross-linked polymers
star like architecture
brush or comb like
architecture
Vulcanised rubber
IPN
Interpenetrated network
Intermolecular interactions
Flexibility of macromolecules
Rigid polymers
Flexible polymers
india-rubber,
polyisoprene
silicon rubber,
poly(dimethyl-siloxane)
Formation of intra- and intermolecular
H-bonds enhances rigidity.
Enlarged distance between rotating units increases the flexibility!
Models of flexible polymers
Highly flexible polymers
Free rotation around C-C bond
d
blob
Random coil.
Short range interactions
(constitution)
Ideal flexible macromolecule
Random walk
r
Conformation
⎛ 1 + cosϑ ⎞
Rϑ = l ⎜
⎟
⎝ 1 − cosϑ ⎠
Valence angle
Ns
r = ∑ ri
< r >= 0
Valence angle
+
Rotation energy
i =1
< r >≠ 0
2
1/ 2
. N 1/ 2
⎛ 1 + cosϑ 1+ < cosϕ > ⎞
Rϑ ,ϕ = 1⎜
⎟
⎝ 1 − cosϑ 1− < cosϕ > ⎠
< cosϕ >=
π
∫π cosϕ . e
1/ 2
−
N 1/ 2
U (ϕ )
RT
dϕ
−
Ns
Ns
Ns
Ns
Ns
i =1
i< j
i< j
r 2 = ∑ ∑ r i r j = ∑ ri 2 + 2∑ ri r j = Na s2 + 2∑ a s2 cos α ij
i =1 j =1
Ro ≡< r 2 >1/2
R0 = as N s1/2
Ideal macromolecule
RΘ = l ⋅ C∞ ⋅ N 1/2 = C∞ R0
RΘ = l ⋅ C∞ ⋅ N 1/2 = as N s1/2
Characteristic ratio
Macromolecules of life
Proteins
Poly(amino acids)
random walk (RW)
R0 = a s N s1/ 2
self avoiding walk (SAW)
R0 = as N νs ν = 0.588 ≈ 3 / 5
Excluded volume effect!
Nucleic acids
RNA and DNA
Glycans
Glycans are sugar
or sugar polymers
Structure of macromolecules
constitution
Tertiary structure (globular proteins):
configuration conformation
Primary structure:
Human’s genom project: complete primary structure of a human’s
DNA molecule
if N ~ 102 and 20 different monomer units, then 20100 different molecules!
Quaternary structure ( association of several chains):
Secondary structure:
Long range order of monomer units
Pl. ceratine,
fibroin
α helix
β structure
Polymer biomaterials
Structures display a hierarchial organisation