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

Metabolism

Metabolism is essential for maintaining life by certain chemical reactions. In the result of these reactions and phenomenon, organisms develop ability to grow and reproduce, while maintaining their structures and adopt itself according to the environment.

Types of Metabolism:
There are two types of metabolism:
1. Catabolism:
Catabolism catabolyze or breaks the organic matter and produce heat or energy as a result.

2. Anabolism
Anabolism utilize the energy produced by the catabolism of organic matter.

Factors important in metabolism:
1. Chemicals
Chemicals are important for the metabolic pathways.

2. Enzymes
These enzymes catalyze a reaction involving the chemicals. They make the environment favourable for a reaction to proceed.

Distribution

Distribution in pharmacology is a branch of pharmacokinetics which describes the reversible transfer of drug from one location to another within the body. It is the movement of molecules of drugs from blood into general body (compartments) and peripheral tissues.

The distribution of a drug between tissues is dependent on permeability between tissues (between blood and tissues in particular), blood flow and perfusion rate of the tissue and the ability of the drug to bind plasma proteins and tissue. pH parturition plays a major role as well.

Once a drug enters into systemic circulation by absorption or direct administration, A drug has to be distributed into interstitial and intracellular fluids.

The lipid solubility, pH of compartment, extent of binding with plasma protein and tissue proteins, cardiac output, regional blood flow, capillary permeability are associated for distribution of the drug through tissues.The drug is easily distributed in highly perfused organs like liver, heart, kidney etc in large quantities & in small quantities it is distributed in low perfused organs like muscle, fat, peripheral organs etc. The drug can be moved from the plasma to the tissue until the equilibrium is established (for unbound drug present in plasma).

The volume of distribution (VD) of a drug is a property that quantifies the extent of distribution.

Further reading:
Comparative Pharmacokinetics: Principles, Techniques, and Applications by Jim E. Riviere

Pharmacokinetics : Principles and Applications by Mehdi Boroujerdi

Clinical Pharmacokinetics Handbook by Larry Bauer