단백질. 1. 단백질은아미노산이라부르는단위체들로구성된선형중합체 2. 단백질은화학반응성이있다 3. 단백질의상호작용으로복잡한구조를만들수있다 4. Rigid 한단백질과 Flexible 한단백질이아미노산의조성에따라존재한다. 5. 중요한효소

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1 단백질 1. 단백질은아미노산이라부르는단위체들로구성된선형중합체 2. 단백질은화학반응성이있다 3. 단백질의상호작용으로복잡한구조를만들수있다 4. Rigid 한단백질과 Flexible 한단백질이아미노산의조성에따라존재한다. 5. 중요한효소

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3 머리스타일을어떻게자유롭게 변경하는가?

4 Permanent Hair Wave ( 머리카락의웨이브?) The formation of disulfide bonds has a direct application in producing curls in hair by the permanent wave process. Hair keratin consists of many protein alpha-helices. Three alpha-helices are interwoven into a left-handed coil called a protofibril. Eleven protofibrils are bonded and coiled together to make a microfibril. Hundreds of these microfibrils are cemented into an irregular bundle called a macrofibril(protein aggregation). These in turn are mixed with dead and living cells to make a complete strand of hair. Although it may seem incredible, in order for hair to grow 6 inches in one year, 9-1/2 turns of a -helix must be produced every second. The alpha-helices are extensively cross-linked with disulfide bonds from cysteine. These bonds enable keratin to have a somewhat elastic nature. If the alpha -helices stretch unevenly past each other, the disulfide crosslinks return them to the original position when the tension is released 단백질구조를모두학습하고다시읽어볼것

5 Disulfide bonds are formed by oxidation of the sulfhydryl groups on cysteine. 단백질구조를모두학습하고다시읽어볼것 Different protein chains or loops within a single chain are held together by the strong covalent disulfide bonds. The alpha-helices in the hair strands are bonded by disulfide links

6 HSCH 2 CO 2 NH 4. ammonium thioglycolate In the permanent wave process, a basic reducing substance (usually ammonium thioglycolate) is first added to reduce and rupture some of the disulfide cross-links. The thiol-disulfide exchange reaction is accelerated by bases such as ammonia, because the base generates some thiolate anion (RS - ), which attacks the disulfide. HSCH 2 COO + NH 4 + HSCH 2 COOH + NH 3 단백질구조를모두학습하고다시읽어볼것

7 Temporary Wave: When the hair gets wet, water molecules intrude into the keratin strands. The sheer numbers of water molecules are able to disrupt some of the hydrogen bonds which also help to keep the alpha-helices aligned. The helices are able to slip past each other and will retain a new shape in the hair drying process as new hydrogen bonds are formed. The hair strands are able for a short time to maintain the new curl in the hair. Permanent Wave: The hair is put on rollers or curlers. Since the alpha-helices are no longer tightly cross-linked to each other, the alphahelices can shift positions in relation to each other. An oxidizing agent, usually a dilute solution of hydrogen peroxide, (also called the neutralizer) is added to reform the disulfide bonds in their new positions. The permanent will hold these new disulfide bond positions until the hair grows out, since new hair growth is of course not treated. 단백질구조를모두학습하고다시읽어볼것

8 단백질의기본아미노산 1. Hydrogen atom, 2. Carboxyl (COO-) group, 3. amino acid (NH3+) group 4. R group, which is different for each amino acid

9 단백질들은 20 개의아미노산들로구성되어있다 pka=9? 중성 ph 용액에서아미노산들은쌍극성이온으로우세하게존재한다. 쌍극자형태에서는 (Zwitterion) NH3+ 와 COO- 로존재한다. 아미노산의이온화는 ph 에따라달라진다 pka=2? NH3+ : 산성용액에서는 ( eg ph 1), 아미노기가양성자화되어있음. 그러나 COOH 로존재, 하지만 ph 가올라가면서 ph=2 일때 COOH 가 COO- 가되어전체적인전하는중성을갖게된다.

10 1. 무극성 R 원자단을갖는소수성아미노산 2. 중성 R 원자단을갖는극성아미노산, 그러나전하는균등하게분포되어있지 않다. 3. 생리적 ph에서양전하를띠는 R 원자단을갖는양전하아미노산들 4. 생리적 ph에서음전하를띠는 R 원자단을갖는음전하아미노산

11 극성 ( 極性 ) 이란두개이상의원자로이루어진어떠한분자내에서전자구름이몰려있는상태를말하는것으로, 비교적고정되어있으며양전하를띠는원자핵이얼마나노출되어있는지로보이기도한다. 특히, 분자가두종류이상의원자로이루어져있을때한쪽핵으로전자가끌려가는경우 ( 간단한예로 H 2 O 의 O 쪽 ) 그부분을 Δ 마이너스, 그반대편을 Δ 플러스로표기하는것으로간단히보이기도한다. 이러한극성은서로다른극이전기적인력을띠게되기때문에높은결합력을보이며, 용해성역시같은극성분자끼리크다. 무극성이란극성이매우적거나, 심하게는없는것을말하는것으로이러한무극성분자는극성분자에비해일반적으로분자간의인력이적으며반데르발스의힘이라는유사극성으로결합력을강화하기도한다. 분자의구조가대칭형인분자들은무극성이다. [1] 무극성분자역시무극성분자끼리의용해성이크다

12 무극성 ( 소수성아미노산 )

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14 극성아미노산 ( 친수성, 물과반응이좋다 )

15 양전하를갖는아미노산

16 음전하

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19 단백질에있는이온화할수있는원자단들의 pka 값들

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22 Ala pka=8.0 pka=3.1 ph= 2.0 ph=5.5,ph= 7.0, ph= 9.0 ph=12???

23 Valine pka=8.0 pka=3.1 ph= 2.0 ph=5.5,ph= 7.0, ph =9.0 ph=12???

24 Met pka=8.0 pka=3.1 ph= 2.0 ph=5.5,ph= 7.0, ph= 9.0 ph=12???

25 Aspartic Acid pka=8.0 pka=3.1 pka=4.1 pi=3.8 ph= 2.0 ph=5.0,ph= 7.0, ph= 9.0 ph=12???

26 Histidine pka=8.0 pka=3.1 pka=6.0 pi=7.0 ph= 2.0 ph=5.0,ph= 7.0, ph= 9.0 ph=12???

27 Cysteine pka=8.0 pka=3.1 pka=8.3 pi=5.0 ph= 2.0 ph=5.0,ph= 7.0, ph= 9.0 ph=12???

28 Tyrosine pka=8.0 pka=3.1 pi=5.7 pka=10.9 ph= 2.0 ph=5.0,ph= 7.0, ph= 9.0 ph=12???

29 Lysine pka=8.0 pka=3.1 pi=9.8 pka=10.8 ph= 2.0 ph=5.0,ph= 7.0, ph= 9.0 ph=12???

30 Arginine pka=8.0 pka=3.1 pka=12.5 pi=10.8 ph= 2.0 ph=5.0,ph= 7.0, ph= 9.0 ph=12???

31 Lysine pka=8.0 pka=3.1 pi=9.8 pka=10.8 1) What fraction of these groups will be protonated in a dilute solution of Lys at ph =9.5? 2) At ph = 11.0? 3) Why pi is higher than 8.0?

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