Fragmentation

In cell biology, fragmentation is the breaking apart of cells or cell organelles into smaller parts. Fragmentation may serve as a normal function for the cell, but may also be the result of a disorder.

Functions of cell fragmentation include:
Reproduction
Apoptosis

Disorders:
Microangiopathic diseases results in red blood cell fragmentation into schistocytes.

Further reading:
Biology: A Self-Teaching Guide, 2nd edition by Steven Daniel Garber

Lorentz force law

It is equal to a force on a point charge due to electromagnetic fields.

It is given by the following equation in terms of electromagnetic fields:

F = q [E + (v x B)]

where,
F = force (in newtons)
E = electric field (in volts per meter)
B= magnetic field (in teslas)
q = electric charge of the particle (in coulombs)
v = instantaneous velocity of the particle (in meters per second)

Dissociation

It is a process in which there is separation of ionic compounds into smaller parts (molecules or ions).

It is usually a reversible process.

It is the opposite of association and recombination.

pKa

pKa is an acid dissociation constant.

Definition:
It is the negative logarithm of the acid dissociation constant i.e., Ka

Equation:
Its equation is:
pKa = -log10 Ka

Importance:
1. It shows the extent of dissociation. As the value of pKa increases, the extent of dissociation will decrease.
2. It has the ability of telling the acidic or basic properties of a substance.

Mass analyzer

Mass analyzer is a technique used for the separation of the ions according to mass/charge ratio.

Equation for the Mass analyzer:

1. Lorentz force law:
F=Q(E+v*B)

Where
F = force applied to the ion
Q = ion charge
E = electric field
v*B = the vector cross product of the ion velocity and the magnetic field

2. Newton's second law of motion:
F=ma

Where
F = force applied to the ion
m = mass of the ion
a = acceleration

By combining the above two equations, we get:

Q(E+v*B) = ma

=> E+v*B = a(m/Q)

where m/Q denotes mass to charge ratio.

Types of mass analyzers:

There are various types of mass analyzers:

1. Scanning Mass Analyzers

2. TOF - Mass Analyzers

3. Trapped Ion Mass Analyzers

Ion Source

It is a type of an electro-magnetic instrument, primarily used to create charged particles.

It is used in ion implanters, ione engines, mass spectrometersand particle accelerators.

Mass spectrometry

Introduction:
Mass spectrometry is a technique used in analysis.

It is a form of spectrometry in which, usually, high energy electrons are bombarded onto a sample and this produces charged particles of the parent sample; these ions are then focused by electrostatic and magnetic fields to produce a spectrum of the charged fragments which is helpful in establishing the ratio of charged to mass of the particles.

Essential parts:
The design of a mass spectrometer has three essential modules:

1. An ion source:
This transforms the molecules in a sample into ionized fragments.

2. A mass analyzer:
This causes the sorting of the ions by their masses by applying electric and magnetic fields

3. A detector:
This measures the value of some indicator quantity and thus provides data for calculating the abundances of each ion fragment present.

Uses and applications:
The technique has both qualitative and quantitative uses, such as

1. Identifying unknown compounds,
2. Determining the isotopic composition of elements in a compound,
3. Determining the structure of a compound by observing its fragmentation. Its use is there in the identification and structural determination of the flavonoid glycosides. ( Maciej Stobiecki)
4. Quantifying the amount of a compound in a sample,
5. Studying the fundamentals of gas phase ion chemistry
6. Determining other physical, chemical, or biological properties of compounds.

It is now applicable in the field of proteomics. (Christine C. Wu et al.)

References:
Christine C. Wu and John R. Yates III, The application of mass spectrometry to membrane proteomics, Nature Biotechnology 21, 262 - 267

Maciej Stobiecki, 2000, Application of mass spectrometry for identification and structural studies of flavonoid glycosides , Phytochemistry, 54, 237-256

Further reading:
Mass Spectrometry: Principles and Applications by Edmond de Hoffman and Vincent Stroobant

Mass Spectrometry: A Textbook by Jürgen H. Gross