1

Temperature dependence of K depends onlyon ∆H0 by the Van’t Hoff equation

Van’t Hoff equation

−

∆−=

12

0

1

2 11lnTTR

HKK

−

∆−=

−

∆−=∴

12

0

12

12

0

1

2

11exp

11exp

TTRHKK

TTRH

KK

361 Lec 19Tue, 3oct17

2

∆G0 = -RTlog (K)

K(T) = e-∆G0/RT

K(T) = e-∆G0/RT = e-(∆H0-T∆S0)/RT

Do NOT assume ∆G0 is independent of T !!!

Temperature dependence of K depends onlyon ∆H0 by the Van’t Hoff equation

WARNING!

3

361 Lec 19Tue, 1oct13

∆G0’ for forming a base pair

4

Table 4.4

Initiation Fees

∆Ginit =+8.1 kJ/mol

∆Hinit =+0.8 kJ/mol

Independent ofsite of initiationand direction ofzipping

Because, ultimately, 1 initiatation and ALL pairing are made, regardless of starting point and direction.

5

All numbers in table are for adding a base pair in the

direction 5’ 3’

Doesn’t matter which strand

6

7

But, 5’ A-C is accidently= 5’ C-A

and 5’ A-G is accidently= 5’ G-A

Independent of which pairs first!

8

Also there are ACCIDENTALEquivalencies

Here A followed by C

is NOT expected to besame as C followed by A

It just happens to be.

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5’...-A-A-...3’3’...-T -T-...5’

180 degreerotation 5’...-A-A-...3’

3’...-T -T-...5’

5’...-A-T-...3’3’...-T-A-...5’

180 degreerotation 5’...-A-T-...3’

3’...-T-A-...5’

NOT 5’...-T-A-...3’3’...-A-T-...5’

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5’...-A-T-A-G-C-A...3’3’...-T-A-T-C-G-T...5’

∆G0 init +8.1 - 3.7 -2.4 -5.4 -9.3 -6.0 = -18.7∆H0 init +0.8 -30.2 -30.2 -32.7 -41.0 -35.6 = -168.9

Example:

This is for FORMING the double strandHomework S2 is for melting the double strand

1416)310(3145.8

700,18exp

exp0

=

−−=

∆−=

K

RTGK

11

12

HA --> A- + H+

Same math as dissociation of weak acid

13

1 nM

nM

14

Like Prob. 14 a (see Example 4.15 p. 133 ) 7 unknowns

need 7 equations

7th equation: Sum of the 4 His species = 0.10 mol

1st equation[H+]=10-pH

2nd equation

3rd equation

4th equation5th equation

6th equation

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Temporarily

Temporarily

Strategy:Find 3 ratios

First work withthe largest ratio

First work withthis FIRST

2 equations 2 unknowns

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Now, go back and solve for the small concentrations that were temporarily ignored