Chapter 32, Problem 32.17QAP

Interpretation Introduction

(a)

Interpretation:

The amount of protein sample hydrolyzed is 10.0g. The specific activity of the ${}^{14}C$ labeled threonine is 1000cpm/mg and the 3.00mg of threonine is added to the hydrolysate. After mixing the specific activity of the threonine is 20cpm/mg when the pure threonine of amount 11.5 mg was isolated. The percentage of protein which is threonine is to be determined.

Concept introduction:

The formula for the half time is given as-

$t_{1/2}=\frac{0.693}{\lambda }$ ………………….. (1)

Where,

$\lambda =decayconstant$

The amount of inactive species is calculated by the isotope dilution method which is given as-

$m_x=\frac{R_t}{R_m}\times m_m-m_t$ ………………………. (1)

Here,

$m_x$ = mass of inactive sample

$R_t$ = counting rate

$R_m$ = counting rate of inactive analyte

$m_m$ = isolated mass which is purified from the mixture of radioactive tracer

$m_t$ = mass of radioactive tracer

Interpretation Introduction

(b)

Interpretation:

The amount of protein sample hydrolyzed is 10.0g. The specific activity of the ${}^{14}C$ labeled threonine is 1000cpm/mg and the 3.00mg of threonine is added to the hydrolysate. After mixing the specific activity of the threonine is 20cpm/mg when the pure threonine of amount 11.5 mg was isolated. The change in the answer is to be determine when the ${}^{11}C$ with half time 20.3 min is used instead of ${}^{14}C$ and the elapsed time for the two specific activity is 32 min.

Concept introduction:

The formula for the half time is given as-

$t_{1/2}=\frac{0.693}{\lambda }$ ………………….. (1)

Where,

$\lambda =decayconstant$

The specific activity of radioactive element is calculated by the following equation-

$A=A_0{e}^{-\lambda t}$

Or

$A_0=A{e}^{\lambda t}$ ……………….. (2)

Where,

A₀ = initial activity

A = final activity

The amount of threonine is calculated by the following formula-

$m_x=\frac{R_t}{R_m}\times m_m-m_t$ ……………………….. (3)

Where,

$m_x$ = mass of inactive sample

$R_t$ = counting rate

$R_m$ = counting rate of inactive analyte

$m_m$ = isolated mass which is purified from the mixture of radioactive tracer

$m_t$ = mass of radioactive tracer