You are trying to determine information about the structure of a protein that you have purified. You carry out a series of experiments

You are trying to determine information about the structure of a protein that you have purified. You carry out a series of experiments on this protein. The results are listed below. 1. Size exclusion (aka gel filtration) chromatography of the protein indicates an apparent molecular weight of 240,000 kDa.
2. SDS polyacrylamide gel electrophoresis of the protein carried out WITHOUT the addition of a disulfide-bond reducing agent shows the protein as having an apparent molecular weight of 60,000 kDa.
3. After treatment with performic acid, which cleaves disulfide bonds, the same technique (SDS PAGE) reveals two bands of molecular weights 34,000 kDa and 26,000 kDa.
4. N-terminus identification shows Ala and Leu as amino terminal residues, in equal amounts.

Describe what you can determine about the protein's structure from the above information by answering the questions below.

a. Molecular weight of the native functional protein.
b. Does the protein contain any disulfide bonds? If yes, can you estimate how many ?
c. Can you determine anything about any secondary structure of the protein? If yes, what?
d. Does the protein have quaternary structure? If yes, how many subunits, of what size?

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  1. Explanation:

    weight average = fraction of A X MW of A + fraction of B x MW of B  

    Mixture 1  

    1 / 3 x 100000 + 2/3 x 400000 = 900000 / 3 = 300000

    Mixture 2

    2/3 x 100000 + 1/3 x 400000 = 600000 / 3 = 200000

    Number average  

    Mixture 1  

    (1 / 100000 x 100000 + 2 / 400000 x 400000) / (1/100000 + 2/400000 )

    = 3 x 400000 / 6  

    = 200000

    Mixture 2  

    (2/100000 x 100000 + 1/400000 x 400000 )/ (2/100000 + 1 / 400000 )

    3 x 400000 / 9  

    =( 4/3 ) x 100000

  2. r= 0.9949 (For 15,000)

    r=0.995 (For 19,000)

    Explanation:

    We know that

    Molecular weight of hexamethylene diamine = 116.21 g/mol

    Molecular weight of adipic acid = 146.14 g/mol

    Molecular weight of water = 18.016 g/mol

    As we know that when  adipic acid  and hexamethylene diamine react then nylon 6, 6 comes out as the final product and release 2 molecule of water.

    So

    [tex]M_{repeat}=146.14+166.21-2\times 18.106\ g/mol[/tex]

    [tex]M_{repeat}=226.32\ g/mol[/tex]

    So

    Mo= 226.32/2 =113.16 g/mol

    [tex]M_n=X_nM_o[/tex]

    Given that

    Mn= 15,000 g/mol

    So

    15,000 = Xn x 113.16

    Xn = 132.55

    Now by using Carothers equation we know that

    [tex]X_n=\dfrac{1+r}{1+r-2rp}[/tex]

    [tex]132.55=\dfrac{1+r}{1+r-2\times 0.99r}[/tex]

    By calculating we get

    r= 0.9949

    For 19,000

    19,000 = Xn x 113.16

    Xn = 167.99

    By calculating in same process given above we get

    r=0.995

  3. Mn=43783 g/mol

    Mw=60000 g/mol

    Mz=73333 g/mol

    Explanation:

    Hello,

    In this case, since the molar masses of the fractions are 20x10³, 40x10³, 60x10³, 80x10³ and 100x10³, the total molar mass is:

    [tex]M_T=20x10^3+40x10^3 +60x10^3+80x10^3+100x10^3=300x10^3g/mol[/tex]

    Now, assuming each fraction weights 1 gram, the moles of each fraction turns out:

    [tex]n_1=\frac{1g}{20x10^3g/mol}=5x10^{-5} mol\\n_2=\frac{1g}{40x10^3g/mol}=2.5x10^{-5} mol\\n_3=\frac{1g}{60x10^3g/mol}=1.7x10^{-5} mol\\n_4=\frac{1g}{80x10^3g/mol}=1.25x10^{-5} mol\\n_5=\frac{1g}{100x10^3g/mol}=1x10^{-5} mol[/tex]

    And the total moles:

    [tex]n_T=11.42x10^{-5} mol[/tex]

    Therefore,

    [tex]Mn=\frac{\Sigma W_i}{n_i} =\frac{5g}{11.42x10^{-5} mol}=43783g/mol[/tex]

    [tex]Mw=\frac{\Sigma W_iM_i }{\Sigma W_i}=\frac{300x10^{3}g/mol}{5} =60000g/mol[/tex]

    [tex]Mz=\frac{\Sigma W_iM_i^{2}}{\Sigma W_iM_i}=\frac{(4x10^8+1.6x10^9+3.6x10^9+6.4x10^9+10x10^9)g^2/mol^2}{300x10^{3}g/mol}=73333g/mol[/tex]

    Best regards.

  4. Mn = 43,783

    Mw = 60,000

    Mz = 73,333

    narrow distribution = 1.37

    Explanation:

    The molecular weights of these fractions increase from 20,000 to 100,000 in increments of 20,000. This means their Mi is respectively: (The molar weight (Mi) of the fractions)

    Fraction 1 : Mi = 20  *10^3

    Fraction 2: Mi = 40 *10^3

    Fraction 3 : Mi = 60 *10^3

    Fraction 4: Mi = 80 *10^3

    Fraction 5 : Mi = 100  *10^3

    The ΣMi = 300*10^-3

    The Wi (mass of the fractions is for all the fractions the same, let's say 1)

    So Wi = 1+1+1+1+1 = 5

    Since number of moles = mass / Molar mass

    The number of moles is respectively: ni = Wi/Mi (x10^5)

    Fraction 1 : ni = Wi/Mi = 1/20000 = 5

    Fraction 2: ni = 1/40000 = 2.5

    Fraction 3 : ni =1/60000 = 1.67

    Fraction 4: ni = 1/80000 = 1.25

    Fraction 5 : ni= 1/100000 = 1

    The Σni = 11.42

    Mn = ΣWi/ni = 5/11.42*10^-5 = 43,783

    Mw = (ΣWi * Mi)/ΣWi  = 300,000 /5 = 60,000

    Mz = (ΣWi * Mi²)/ΣWi *Mi = (4*10^8 +16*10^8 +36*10^8 +64*10^8 +100*10^8) /300,000  =73,333

    Mz/Mn = narrow distribution =60,000/43,783 = 1.37

  5. Explanation:

    1.The particles move faster, and their average kinetic energy increases.

    If the temperature of gases are increase, the gas particles will gain more kinetic energy and they will begin to move randomly and haphazardly in the container that contains them. Temperature is directly proportional to increase in kinetic energy of gases.

    2. The entire container because gases will expand to fill it.

    Gases fills up containers and they assume the volume and shape of wherever they are put into. Therefore, the volume of occupied by a gas is actually the volume of the container they occupy. Gases are able to do this because they are free.

    3. Because the attractive forces between gas particles are negligible, gas particles can glide easily past one another.

    Gases acts fluid because they have little to no intermolecular attraction between them. Therefore they have low density and close to zero packing. This makes them easily glide past one another and this is why they act fluid.

    4. Solid

    Solids are arranged in a particular pattern. The molecules are close together and they vibrate about a fixed position. Ordered arrangements of particles of solid gives them their unique shapes.

    5. Gas particles spread out to fill a container, leading to a low density of the gas.

    Density is defined as the amount of substance i.e mass per unit volume. If you have more mass occupying a particular volume, then density will be high. For gases, they move to fill the containers that houses them and so they have low density.

    6. Solids have low compressibility compared to liquids.

    Gases are the most compressible form of matter. Solids are not easily compressible because their particles have a well ordered arrangement. Solids are rigid and do not readily move. Therefore, they readily restrain compressive forces on them. Liquids molecules moves about within the liquid. They are slightly compressible.

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