Enzyme
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enzyme. 最好有緩衝液存可使得反應最大. α-Chymotrypsin catalyzed cleavage of the C-N bond has a maximum rate near pH 8 that is twice as great as the rate near pH 7 or pH 9. 2.細胞培養一般步驟,資列以 Human fibroblasts 作為例子 Cultures for Human fibroblasts (HF, doubling time = 24 h)

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Enzyme

enzyme


Enzyme

最好有緩衝液存可使得反應最大

α-Chymotrypsin catalyzed cleavage of the C-N

bond has a maximum rate near pH 8 that is twice

as great as the rate near pH 7 or pH 9.


Enzyme

2.細胞培養一般步驟,資列以Human fibroblasts作為例子Cultures for Human fibroblasts (HF, doubling time = 24 h)

A. DMEM 培養液1. 5X DMEM medium 100 ml2. 100X Glutamic acid 5 ml3. 100X streptomycin / penicillium 5 ml4. 5.5% NaOHCO3 10-20 ml 5. Hyclone fetal calf serum (FCS, 56C, 30min ) 50 ml6. Hepes 緩衝液(1.5 M pH=7.4) 5 ml

7. 加 ddH2O 至 500ml


Enzyme

The Henderson-Hasselbalch Equation

HA= H++ A-

Ka=[H+]*[A-]/[HA]

[H+]=Ka*[HA]/[A-]

-log[H+]=-logKa – log( [HA]/[A-])

pH=pKa + log([A-]/[HA]

Henderson-Hasselbalch Equation for an acid

可應用在處理酸鹼平衡系統並用來配製緩衝溶液。當共軛酸鹼的濃度相同時,則pH=pKa


Enzyme

緩衝溶液就是對於外界添加酸或鹹至溶液中,其pH值的變化量不大,而當溶液處於pKa時,則具大的緩衝能力。

下圖胺基丙酸(alanine)水溶液在pKa值2.74及9.8時有最大的緩衝能力,在等電點(PI)時緩衝能力最低,溶於水時,胺基丙酸帶有未質子化的羧基(-COO-)及質子化的胺基(-NH3+),pH值等於6,約為兩者之pKa中間,其滴定曲線如圖。


Enzyme

The Henderson-Hasselbalch Equation for a base

B + H2O = BH+ + OH-

Kb=[BH+]*[OH-]/[B]

log kb=log([BH+]/[B])+log[OH-]

log Kw – log Ka = log([BH+]/[B])+log[OH-])

pKa-log ([BH+]/[B])= log[OH-]-log Kw

pKa+log([B]/BH+)=-(- log[OH-]-log Kw=-pOH+14

pH= pKa+log([B]/[BH+])


Enzyme

  • 土壤的缓冲性能有哪些?

  • 土壤的緩衝性質是指當外界環境產生巨大變動時,土壤仍能維持其大部分之原來性質或只是略微變動而已,而土壤具緩衝能力的多寡主要與土壤的粘粒及有機質含量有關,粘粒及有機質含量越高者,其緩衝能力越高。此緩衝性質可用來說明當添加大量石灰於土壤時,土壤的酸鹼性並不會造成巨大的改變,而施肥時也有類似的結果。


Enzyme

常用的緩衝劑叫tris

依附錄B BH+的Ka=8.075

Tris hydrochloride BH+Cl-

BH+Cl-=BH++Cl- BH+=B+H+


Enzyme

NaOCl溶於水中調緩衝至pH6.2,

[OCl-]/[HOCl]=?

HOCl=H++OCl-,pH=pKa+([OCl-]/[HOCl])

6.2=7.53+log ([OCl-]/[HOCl])

[OCl-]/[HOCl]=10^(6.2-7.53)=0.047


Enzyme

溶解12.43克的tris(FM 121.136)及加4.67克的tris chloride (FM 157.597)於1升水中的pH

12.43/21.36=0.01026 M=tris=B

4.67/157.597=0.0296 M=BH+

pH=pKa+log([B]/[BH+])

=8.075+log(0.0126/0.0296)

=8.61


Enzyme

加12mL 1.0 M HCl入前頁的溶液中,pH?

當強酸加入弱鹼時,幾乎完全反應至BH+

B + H+ = BH+

tris From HCl

moles 始0.1026 0.012(0.012L*1M)

末0.1026 0 0.0296

-00.012 +0.012

0.0906 0.0416

pH=pKa+log(0.0906/0.0416)=8.41

若加入沒有緩衝能力的液體則pH=1.93


Enzyme

最後體積為250毫升,pH 7.6,內含10克的tris hydrchloride (BH+,FW=157.597, BH+ 的pKa =8.075),須添加多少毫升的0.5M NaOH。

10 /157.597=0.0635 mol

BH+ + OH- = B

始 0.0635 x 0

末 0.0635-x 0 x

pH=pKa + log (mol B/ mol BH+)

7.6=8.075+log(x/(0.0635-x)

10-0.475=x/(0.0635-x)=0.335 x=0.0159 mol

0.0159/y=0.5 y=0.0318 L=31.8 mL


Enzyme

A buffer resists changes in pH because the added

acid or base is consumed by the buffer. As the buffer

is used up, it becomes less resistant to changes in pH.


Enzyme

pH=pKa maxmum buffer capacity

The useful pH range of a buffer

is usually considered to be pKa±1

pH value


Enzyme

練習 HA=H+ + A-

Ka=10^-5 HA+A-=1

0.01 H+ OH- 加入 新的pH形成。 △pH=pH的改變

例如:混合0.0383mol 的A- 及 0.9617 mol的HA起始

的pH3.6, 加人0.01 mol的OH- 則pH的改變 pH=3.705

3.705-3.6=0.105


Enzyme

  • 2.細胞培養一般步驟,資列以Human fibroblasts作為例子Cultures for Human fibroblasts (HF, doubling time = 24 h)

  • A. DMEM 培養液1. 5X DMEM medium 100 ml2. 100X Glutamic acid 5 ml3. 100X streptomycin / penicillium 5 ml4. 5.5% NaOHCO3 10-20 ml 5. Hyclone fetal calf serum (FCS, 56C, 30min ) 50 ml6. Hepes 緩衝液(1.5 M pH=7.4) 5 ml

  • 7. 加 ddH2O 至 500ml


Enzyme

溴甲酚綠 在 pH小於4.7為黃色,大於4.7為藍色

acid-base indicator

pH=pKa maxmum buffer capacity


Enzyme

瑞香草酚藍, pH小於1.7為紅色,1.7-8.9為黃色,

大於8.9為藍色


Enzyme

以Thymol blue 為例

Transition range Acid Base

color

Thymol blue 1.2-2.8 Red Yellow

8.0-9.6 Yellow Blue

R= Y- + H+ pH=pK1+log([Y-]/[R])

當pH=1.7(=pk1)1:1比例 green

[R]/[Y-]大於等於10/1(pH=0.7) red

[Y-]/[R]大於等於10/1(pH=2.7 yellow

pH8-9.6 為綠色 小於8為黃色 大於9.6為藍色


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