DR . R. MAHENDIRAN RAMASAMY

 It is an instrument used to measure the amount of absorbance of light by a sample.  It is used to measure the absorbance of light by placing samples in a cuvette in the instrument  It was invented by Arnold J. Beckman and his colleagues at National Technologies Laboratory (NTL) in 1940. Principle: It is used to measure the light intensity as a function of wavelength. The diffraction of light by a prism into different wavelengths was detected by the charged couplers or detectors. Instrumentation: Energy source Monochromator- used to break polychromatic radiation into its component wavelengths. Prism- types used are 600 Cornu quartz prism and 300 Littrow prism. Grating- used in monochromators of instruments operating in the ultraviolet, visible, and infrared regions. Cuvettes- It is made up of quartz material where the samples are loaded and placed in the instrument for operation. Detector- It is based on photoelectric current and is amplified and recorded. Applications: d...

  Centrifugation  is a term used to describe a method of separating mixtures using spinning and centrifugal force. Several characteristics can separate particles during centrifugation, including size, shape, density, and viscosity. British military engineer Benjamin Robins, who built a device that resembled an arm rotating around an axis to gauge drag on items. The Prandtl brothers later made the first practical centrifuge to separate milk from the cream by improving this design. By rapidly rotating a container containing material, separation is accomplished, the centrifugal force forces heavier elements to the outside of the container. Principles of Centrifuge: The centrifuge utilizes the sedimentation principle due to gravitational force. The centrifugation technique uses a centrifugal field to separate particles suspended in a liquid medium. These are put in the centrifuge’s rotor either in bottles or tubes. Sedimentation is a process in which gravity causes suspended parti...

An autoclave is a machine that provides a physical method of sterilization by killing bacteria, viruses, and even spores present in the material put inside the vessel using steam under pressure. Autoclave Principle/ Working The autoclave works on the principle of moist heat sterilization, where steam under pressure is used to sterilize the material present inside the chamber. The high pressure increases the boiling point of water and thus helps achieve a higher temperature for sterilization. Water usually boils at 100°C under normal atmospheric pressure (760 mm of Hg); however, the boiling point of water increases if the pressure is increased. Similarly, the high pressure also facilitates the rapid penetration of heat into deeper parts of the material, and the moisture present in the steam causes the coagulation of proteins, causing an irreversible loss of function and activity of microbes. This principle is employed in an autoclave where the water boils at 121°C at the pressure of 15 ...

  REAL TIME PCR   AIM:  Demonstration of Real-Time PCR through experimental samples  INTRODUCTION:  Real-time quantitative PCR allows the sensitive, specific and reproducible quantitation ofnucleic acids. It monitors the amplification of a targeted DNA molecule during the PCR (i.e.in real time), not at its end, as in conventional PCR. Real-time PCR is the technique ofcollecting data throughout the PCR process as it occurs, thus combining amplification and detection into a single step. Using PCR, specific sequences within a DNA or cDNA template can be copied, or “amplified”, many thousand- to a million-fold using sequence specific oligonucleotides, heat stable DNA polymerase, and thermal cycling. The PCR is the cyclic reaction based on the rapid change in temperature during each step. During PCR, our gene of interest is amplified as well as quantified. Real-time quantitative PCR is the reliable detection and measurement of products generated during each cycle of...

  I SOL A T I ON A N D SE P ARA T I ON OF C H R O M OSO MA L D N A FR OM B A C TE R I A   AI M : To iso l a te a nd s e p a r a te t h e c h r omosomal D N A f r o m ba c te r ia   P RI N C I P LE:   G e nom i c ( c h romosomal) D N A f rom e i t h e r b ac t e r ia, plant or a ni m a l ce ll c a n be iso l a ted b y l y sis m e thod. F or pl a nt ce ll or b ac t e ri a l c e l l , f i rst ce ll w a ll is me c h a nic a l l y disrupted. The ce ll w a ll is b r o k e n e n z y ma t ic a l l y using e n z y m e s l i ke l y so z y me. W h e n b a c te r ia a r e l y s e d und e r a lkaline c ondi t ions both D N A a nd p r oteins a re p rec ip i tat e d. A f ter the a ddi t i on of ace tate- c ontaining n e utr a l iz a t i on buf f e r the la r ge a nd le s s supe rc oi l e d c h r omos o mal D N A a nd p rot e ins p rec ip i tat e , but the small b ac te r ial D N A plasmids ca n r ...

  CAPSULE STAINING INTRODUCTION: The main purpose of capsule stain is to distinguish capsular material from the bacterial cell. A capsule is a gelatinous outer layer secreted by bacterial cell and that surrounds and adheres to the cell wall. Most capsules are composed of polysaccharides, but some are composed of polypeptides. The capsule differs from the slime layer that most bacterial cells produce in that it is a thick, detectable, discrete layer outside the cell wall. The capsule stain employs an acidic stain and a basic stain to detect capsule production. AIM : To prepare a smear of an encapsulated bacterium and stain it’s capsule and to visualize the capsule and to differentiate the capsule from the cell body. PRINCIPLE: Capsules stain very poorly with reagents used in simple staining and a capsule stain can be, depending on the method, a misnomer because the capsule may or may not be stained. Negative staining methods contrast a translucent, darker colored, back...