Pharmaceutical Applications of Raman Spectroscopy

             Slobodan Sasic, Sean Ekins, "Pharmaceutical Applications of Raman Spectroscopy"
                                             English  | ISBN: 0813810132 | 286 pages

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Biotechnology in Healthcare

• Publisher: Pharmaceutical Press (12 Oct 1998)
• Language: English
• ISBN-10: 0853693722
• ISBN-13: 978-0853693727

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QSAR - Hansch Analysis and Related Approaches

QSAR: Hansch Analysis and Related Approaches  Publisher: Wiley-VCH | ISBN: 352730035X 

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PHARMACEUTICAL PACKAGING TECHNOLOGY

 
       PHARMACEUTICAL PACKAGING TECHNOLOGY
                                                         
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Carotenoids

Carotenoids 

(A group of highly specialized tetraterpenoids)

Introduction

These are fat soluble or yellow pigments present in plants & animals including bacteria these may be present along with chlorophyll (carotene & lutein) or may be present without chlorophyll. The carotenoid acts as photo sensitizer in conjugation with chlorophyll. When chlorophyll is absent (Fungi), then the carotenoids are mainly responsible for color. Carotenoids are also known as Lipochromes or chromo lipids because they are fat soluble pigments. They give a deep blue color with conc. H₂SO₄ & with a chloroform solution of antimony trichloride this Carr-Price reaction is the basis of the one method of the quantitative estimation of carotenoids. Some carotenoids are hydrocarbons, these are known as carotenes. Other carotenoids are oxygenated derivatives of the carotenes these are xanthophylls. These are also xanthophyll esters which are the natural ester of hydroxy carotenoids.

                                 Examples carotenoid & xanthophyll pigments from plants

Finally, there are some natural polyenes which contain fewer than 40 carbon atoms but structurally related to carotenoids. These are generally classified as the apocarotenoids & contains aldehyde or carboxyl group e.g. bixin (Annatto), Crocetin. When the loss of carbon atoms occurs at one end of the C₄₀ chain, this is shown by a numeral which follows the prefix apo & indicates the last carbon atom remaining from the present carotenoids e.g. β-apo-12 carotenal.

Carotenoid in fungi

These are tetraterpenoids main structure shows highly branched carbon skeleton composed of isoprene units, the center of molecule is formed by linkage of two isoprene unit tail to tail while others are head to tail. Hence central portion of molecule has 1, 6   position of methyl groups. Structurally these are polyenes having long conjugated chain in center of molecule. This portion which has extended conjugation is responsible for color of carotenoids of at the two ends are present two open chain structure or one open chain & other ring or two ring structure. Hence the basic structure of carotenoids becomes

Carotenoids are also known as Lipochromes or chromo lipids because they are fat soluble pigments. Carotenoids comprise of an important & unique class of carotenoids (C-40 terpenoids) in which two methyl group nearest the center of molecule are in position 1:6 while all the  other side chain methyl group occupies 1:5 position. Due to present of 3 isoprene units in structure they may also be regarded as tetra terpenoid. 

Enzyme Immobilization

Enzyme Immobilization

Microbial enzymes are most extensively employed in the food and beverage industries across the globe to meet the ever increasing demand for nutritionally superb and high-value products. In actual practice, the soluble enzymes engaged in ‘batch operations’ is found to be not-so-economical due to the fact that the active enzyme is virtually lost (not recovered) after each viable reaction. Therefore to overcome this problem we are immobilized enzymes after reaction & reuse them.

Immobilized enzymes have been defined as enzymes that are physically confined or localized, with retention of their catalytic activity, and which can be used repeatedly and continuously and the process is called enzymes immobilization.

There is a variety of methods by which enzymes can be localized, ranging from covalent chemical bonding to physical entrapment however they can be broadly classified as follows:

1. Covalent bonding of the enzyme to a derivatized, water-insoluble matrix.

2. Intermolecular cross-linking of enzyme molecules using multi-functional reagents.

3. Adsorption of the enzyme onto a water-insoluble matrix.

4. Entrapment of the enzyme inside a water-insoluble polymer lattice or semi-permeable membrane

Advantages of Enzyme Immobilization

(1) Enzymes being quite expensive and also having the unique ability to be used repeatedly only in a situation when these may be recovered completely from the accomplished reaction mixtures. In true sense, immobilization distinctly and specifically allows their repeated usage by virtue of the fact that such enzyme preparation may be separated conveniently from the reaction system involved.

(2)     Importantly, the final desired product should be readily from the enzyme. It goes a long way in affecting reduction and saving upon the cost of ‘downstream processing’ of the ensuing end-product.

(3)     Non-aqueous systems (i.e., using organic solvents exclusively) are found to be fairly compatible with the immobilized enzymes particularly, and this may be regarded to be extremely desirable in certain typical and specific instances.

(4)     Immobilized enzymes may be used predominantly in most continuous production systems; and, of course, this not absolutely feasible and possible with the ‘free-enzymes’.

(5)     Immobilized enzymes, a few selected ones, may exhibit thermo stability of the highest order, viz., the free-enzyme glucose isomerase usually gets denatured only at 45°C in solution ; however, when immobilized suitably the enzyme is found to be stable enough up to 1 year at 65°C.

(6)     Importantly, the ultimate recovery of ‘immobilized enzyme’ would drastically minimize the high effluent disposable problems (which is quite acute in several fermentation industries).

(7) Immobilized enzymes may be employed at a much higher concentration range in comparison to the corresponding free enzyme.

Disadvantages of Enzyme Immobilization

Immobilized enzymes do offer several disadvantages which are briefly discussed in the section that follows:

(1) Enzyme immobilization evidently gives rise to an additional bearing on cost. Hence, this improved technique is got to be used only in such an event when there prevails a sound economic viability, feasibility, safety, and above all a positive edge over the corresponding ‘soluble enzymes’.

(2)             Immobilization of enzymes invariably affects the stability and or activity adversely. In order to circumvent such typical instances one may have to adhere strictly to the laid down developed immobilization protocols

(3)            Practical utilization of the ‘immobilized enzymes’ may not prove to be of any use or advantage when one of the substrates is found to be insoluble.

(4)             Certain immobilization protocols do offer a good number of serious problems with respect to the diffusion of the ensuing substrate to have an access to the corresponding enzyme.

Tumor suppressor gene

Tumor suppressor gene

Introduction

A tumor suppressor gene, or anti-oncogene, is a gene that protects a cell from one step on the path to cancer. When this gene is mutated to cause a loss or reduction in its function, the cell can progress to cancer, usually in combination with other genetic changes.

Two-hit hypothesis

Unlike oncogenes, tumor suppressor genes generally follow the 'two-hit hypothesis', which implies that both alleles that code for a particular gene must be affected before an effect is manifested. This is due to the fact that if only one allele for the gene is damaged, the second can still produce the correct protein. In other words, mutant tumor suppressor’s alleles are usually recessive whereas mutant oncogene alleles are typically dominant. The two-hit hypothesis was first proposed by A.G. Knudson for cases of retinoblastoma. Knudson observed that the age of onset of retinoblastoma followed 2nd order kinetics, implying that two independent genetic events were necessary. He recognized that this was consistent with a recessive mutation involving a single gene, but requiring biallelic mutation. Oncogene mutations, in contrast, generally involve a single allele because they are gain of function mutations. There are notable exceptions to the 'two-hit' rule for tumor suppressors, such as certain mutations in the p53 gene product. p53 mutations can function as a 'dominant negative', meaning that a mutated p53 protein can prevent the function of normal protein from the un-mutated allele. Other tumor-suppressor genes that are exceptions to the 'two-hit' rule are those which exhibit haploinsufficiency. An example of this is the p27Kip1 cell-cycle inhibitor, in which mutation of a single allele causes increased carcinogen susceptibility.

Functions

Tumor-suppressor genes, or more precisely, the proteins for which they code, either have a dampening or repressive effect on the regulation of the cell cycle or promote apoptosis, and sometimes do both. The functions of tumor-suppressor proteins fall into several categories including the following:

1. Repression of genesthat is essential for the continuing of the cell cycle. If these genes are not expressed, the cell cycle will not continue, effectively inhibiting cell division.
2. Coupling the cell cycle to DNA damage. As long as there is damaged DNA in the cell, it should not divide. If the damage can be repaired, the cell cycle can continue.
3. If the damage cannot be repaired, the cell should initiate apoptosis (programmed cell death) to remove the threat it poses for the greater good of the organism.
4. Some proteins involved in cell adhesion prevent tumor cells from dispersing, block loss of contact inhibition, and inhibit metastasis. These proteins are known as metastasis suppressors.

Examples

The first tumor-suppressor protein discovered was the Retinoblastoma protein (pRb) in human retinoblastoma; however, recent evidence has also implicated pRb as a tumor-survival factor.

Another important tumor suppressor is the p53 tumor-suppressor protein encoded by the TP53 gene. Homozygous loss of p53 is found in 70% of colon cancers, 30–50% of breast cancers, and 50% of lung cancers. Mutated p53 is also involved in the pathophysiology of leukemias, lymphomas, sarcomas, and neurogenic tumors. Abnormalities of the p53 gene can be inherited in Li-Fraumeni syndrome (LFS), which increases the risk of developing various types of cancers.

PTEN acts by opposing the action of PI3K, which is essential for anti-apoptotic, pro-tumorogenicAktactivation. Other examples of tumor suppressors include APC and CD95.