Bhasmas as nanoparticles

➢ Gold in traditional Indian Ayurvedic medicine as Swarna bhasmas(gold ash) has been characterized as globular particles of gold with average size between 56 to 57 nanometre(nm). Also, Swana Bhasma and gold nanoparticles(NPs) prepared by modern method are quite comparable with respect to transmission electronic microscopy(TEM).
➢ Ras-Sindor (sublimed mercury compound) containing mercury sulphide has nanocrystalline size between 25 to 50 nm and is associated with several organic macromolecules derived from plant extract used during processing of drug.
➢ Nanoparticle size of Ayurvedic ‘bhasmas’ has been confirmed in another study where it is proposed that NPs are responsible for its fast and targeted action and subsequent action upon DNA/RNA molecule and protein synthesis within the cell.
➢ Physicochemical characterization of ‘yashada’ (Zinc) bhasma’ using modern are in oxygen deficient state and are in nanometer size range.


“Now, studies have also established that manufacturing methods of Bhasma are in tune of nanotechnology of modern era and bhasmas are nearer to nanocrystalline materials, similar in physico-chemical properties,” he added.
It may be mentioned here that Chaudhary, along with Prasanta Kumar Sarkar of department of Rasa Shashtra, JB Roy State Ayurvedic College, Kolkata have come up with research paper on ayurvedic bhasma after a number of studies in the subject for the past two years. Also, Neetu Singh, research scholar, department of Rasa Shashtra, is also working on the potential of ‘lauha bhasma’ (Bhasma containing traces of iron) in therapeutics, using nanomedicine.

All ‘bhasmas’ have some common properties like ‘rasayana’ (immuno-modulation and anti-aging quality) and ‘yogavahi’ (ability of drug carry and targeted drug delivery). These are prescribed in very minute dose (15 to 250 mg/day) and if prepared properly they are readily absorbable, adaptable and assimilate in the body without being toxic.

“These attributes of bhasmas are comparable with the action of NPs in the body which are also biodegradable, biocompatible and non-antigenic in nature,” Chaudhary said while comparing their properties.

Nanotechnology In Healthcare

KEY: 
•Provides an analysis of market data (revenues) of healthcare nanotechnology applications in North America, Europe, Asia and Rest of World that includes Middle East, Africa, Russia, Latin America and Australia.
• Studies key market drivers and restraints for the main market and evaluation of respective sub segments with respect to market dynamics.
• Discusses drug delivery and formulations, biocompatible implants, regenerative medicine and wound care and diagnostics under the applications market along with related sub segments.
• Nanotechnology initiatives by developing countries are helping in the development of new products and applications.
• The delay in commercialization due to strict regulations and manufacturing difficulties is inhibiting product reach.
• Stability of nanoparticles inside the biological tissues is an important issue to be considered to reduce contamination by drugs.
• The development of biodegradable nanostructures will be a growth driver in future since they eliminate the issue of excretion.

 
SCOPE:
 • Understanding the existing and emerging applications of healthcare nanotechnology and their relative and forecast market sizes
• Understanding the product/technological developments on which the companies are focusing for their growth.
• Understanding the different nanotechnology based tools and their importance in the development of new products and applications

Nanoshell structures

Scientists from four U.S. universities have created a way to use Rice University's light-activated nanoshells as building blocks for 2-D and 3-D structures that could find use in chemical sensors, nanolasers and bizarre light-absorbing metamaterials. Much as a child might use Lego blocks to build 3-D models of complex buildings or vehicles, the scientists are using the new chemical self-assembly method to build complex structures that can trap, store and bend light.



Nanoshells, the building blocks that were used in the new study, are about 20 times smaller than red blood cells. In form, they resemble malted milk balls, but they are coated with gold instead of chocolate, and their center is a sphere of glass. By varying the size of the glass center and the thickness of the gold shell, Halas can create nanoshells that interact with specific wavelengths of light.

"Nanoshells were already among the most versatile of all plasmonic nanoparticles, and this new self-assembly method for complex 2-D and 3-D structures simply adds to that," said Halas, who has helped develop a number of biological applications for nanoshells, including diagnostic applications and a minimally invasive procedure for treating cancer.

The new self-assembly method developed by Capasso's team was also used to make magnetic three-nanoshell "trimers." The optical properties of these are described in the Science paper, which also discusses how the self-assembly method could be used to build even more complex 3-D structures.

Buckyballs and Nanotubes

A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs, and cylindrical ones are called carbon nanotubes or buckytubes.

Because of their unique properties, nanotubes and buckyballs open a path to many futuristic applications. Because of their size, they pose a risk to human health.

Nanotechnology is a broad term that covers many areas of science, research and technology. In its most basic form, it can be described as working with things that are small. Things so tiny that they can't be seen with standard microscopes. The same stuff that has always been there, but we just couldn't see it. The building blocks of nature, atoms and molecules. Nano-technology involves understanding matter at the "nano" scale.

plasmonic nanobubble

The key elements of plasmonic nanobubble research:

1. Plasmonic nanobubbles: laser pulse and plasmonic nanoparticle-generated transient event with tunable optical and mechanical properties.
2. Physical and optical properties of plasmon nanoparticles at high temperatures and in multi-phase environment.
3. Methods for imaging and characterization of plasmon nanoparticles.
4. Heat transfer at nano-scale.Interaction of plasmonic nanobubbles with living cells and tissue.
5. Zebrafish: optically transparent organism as a model for plasmonic nanomedicine

The key elements of cell theranostics:

1. Cell theranostics: dynamically tuned intracellular plasmonic nanobubbles combine diagnosis (through optical scattering), therapy (through mechanical, nonthermal and selective damage of target cells) and optical guidance of the therapy into one fast process.
2.  High-sensitive imaging and diagnosis of cells with plasmonic nanobubbles that may provide up to 102-3-fold increase in sensitivity compared to gold nanoparticles and 105-6 fold increase in sensitivity compared to fluorescent molecules.
3. Targeted therapy with plasmonic nanobubbles: LANTCET (laser activated nano-thermolysis as cell elimination technology). Applicastions: treatment of leukemia and of superficial tumors.
4. Controlled release and intracellular delivery of therapeutic and diagnostic agent into the cells.
5. Methods for imaging plasmonic nanoparticles in living cells and in tissue.
6. Micro-surgery with plasmonic nanobubbles: recanalization of occluded coronary arteries

PLASMONIC NANOBUBBLES

plasmonic nanobubbles, generated around gold nanoparticles with a laser pulse, can detect and destroy cancer cells in vivo by creating tiny, shiny vapor bubbles that reveal the cells and selectively explode them. The nanobubbles have been tested in theranostics with live human prostate cancer cells, without harming the animal host.

Lapotko and his colleagues developed the concept of cell theranostics to unite three important treatment stages -- diagnosis, therapy and confirmation of the therapeutic action -- into one connected procedure. The unique tunability of plasmonic nanobubbles makes the procedure possible. Their animal model, the zebra fish, is nearly transparent, suiting in-vivo research.

Nanotech

Nanotechnology happens in many fields of science. Nano-tech is anything having to do with the development of organic or inorganic devices and materials, including self-assembling molecular "machines" 100 nanometers or smaller in size.

A nanometer is a unit of measurement (abbreviated nm) equal to one billionth of a meter. The term millimicron (symbol mµ), is now considered out of date, but it may still be found in scientific papers.

Consider structures that are only 1/1000th the width of a human hair and smaller, to begin visualizing or imagining the scale of the nano-realms.

Like  other science and technology lenses, this lens is intended to be an overview, a learning center and an outline. It is here to be a general future reference for my self-education and science .

A new technology forces nanoparticles to clump into sewage sludge instead of flowing into aquatic environments.

A single pentacene molecule has been imaged in vivid detail, with even its individual chemical bonds visible - amazing!
 

The power of 'Nano'!

A nanometer (nm) is one-billionth of a meter(much smaller than the visible wavelength of light.) Nanotechnology is the engineering of matter at the molecular scale, and the fabrication of devices or materials in this range of size.

It has a potential wide range of applications in agriculture, industry, communications, medicine etc. Already, nanotechnology is being used commercially; for example, sunscreens made with nanotechnology do not give a whitish tinge when applied to the skin. Nanoparticles in glass screens breaks down when UV radiation falls on it, loosening the dirt on its surface, thus making it self cleaning. A chemical coating of nanoparticles on a car windscreen can make water roll down as tiny droplets, thus improving visibility even in a heavy downpour.

Since the size of nanomaterials are similar to that of most biological molecules and structures, nanomaterials can be useful in medical research and applications.

A futuristic microchip when placed in a tumor mass can collect information on the presence or absence of metastatic cells, thus determining if more aggressive cancer therapy is required or not. Novel nanostructures can help in Parkinson's disease and cardiovascular disease. Artificial tissues can be made to replace diseased kidneys, livers, and nerves. Nervous system integrated nanodevices could restore vision, hearing, and make more efficient prosthetic limbs.

Nanomedicine For Cancer

Before going to the gym for a workout or after indulging in cake at the office party, people with diabetes can use a portable monitor to take a quick blood glucose measurement and adjust their food or insulin intake to prevent extreme dips or spikes in blood sugar. The inexpensive finger-prick testing devices that allow diabetics to check their glucose levels throughout the day may sound like small conveniences. That is unless you are diabetic and can remember back a decade or more, when having that disease came with far more fear and guessing and far less control over your own well-being.

The quality of life afforded to diabetics by technologies that easily and inexpensively extract information from the body offers a glimpse of what all medicine could be like: more predictive and preventive, more personalized to the individual's needs and enabling more participation in maintaining one's own health. In fact, we believe that medicine is already headed in that direction, largely because of new technologies that make it possible to acquire and analyze biological information quickly and cheaply.

NANOROBOTICS

The development of nanorobots is an emerging field with many aspects for further investigations. Simulation is an essential tool for exploring alternatives in the organization, configuration, motion planning, and control of nanodevices exploring the human body. Basically, we may observe two distinct kind of nanorobot utilization. One is nanorobots for the surgery intervention, and the other is nanorobot to monitor patients’ body.

The nanorobots require specific controls, sensors and actuators, basically in accordance with each kind of biomedical application. Many of such required nanodevices are being built nowadays in different research centers around the globe, as well as the necessary control specifications

Nanopore

A nanopore is created in graphene to form a trans-electrode, measuring variations in current as a single DNA molecule passes through the pore.

Oxford Nanopore Technologies today announced an exclusive agreement with Harvard University's Office of Technology Development for the development of graphene for DNA sequencing. Graphene is a robust, single atom thick 'honeycomb' lattice of carbon with high electrical conductivity. These properties make it an ideal material for high resolution, nanopore-based sequencing of single DNA molecules.

"Graphene is emerging as a wonder material for the 21st century and recent research has shown that it has transformative potential in DNA sequencing." said Dr Gordon Sanghera, CEO of Oxford Nanopore Technologies. "The groundbreaking research at Harvard lays the foundation for the development of a novel solid-state DNA sequencing device. We are proud to partner with the research team that pioneered early nanopore discoveries and continues to break boundaries with new materials and techniques.

"Oxford Nanopore is probably best known for protein nanopores," continued Dr Sanghera. "However, today's agreement highlights that we are increasing our investment in solid-state nanopores by adding graphene to our existing portfolio of solid-state nanopore projects and collaborations."

Nanotubes

                    Nanotube formation in a vesicle containing two droplets (PEG - dark, and dextran - green). The membrane is labelled in red. After deflation of the vesicle, nanotubes form within the PEG-rich phase and accumulate at the interface between the two droplets. (a-c) Vertical cross sections of the vesicle; (d) top view of the nanotubes located at the interface. © Max Planck Institute of Colloids and Interfaces

                 Tubular membrane structures can be found in many areas of a cell: in the Golgi apparatus, a type of sorting station in which transport vesicles are formed; in the mitochondria, the power plants of the cell; or in the endoplasmic reticulum, a type of duct network within cells. The tubes have a diameter ranging from a few nanometres (one millionth of a millimetre) to a few micrometres (one thousandth of a millimetre).

            The thinner the tubes, the greater the surface to volume ratio. They are therefore ideal for storing a lot of membrane in rather small spaces. Researchers believe that motor proteins can use energy to pull nanotubes from cellular membranes. “However, motor proteins are not always found in the areas of the cell where membrane nanotubes are formed,” says Rumiana Dimova, a researcher at the Max Planck Institute of Colloids and Interfaces and co-author of the study. For this reason, she believes that there must be another mechanism to generate stable nanotubes.

                The Potsdam-based researchers may have now found the answer to the riddle. “The mechanism generates stable nanotubes without forces having to be exerted on the membrane. It therefore seems to work without the need for motor proteins,” says Dimova. Part of the mechanism is based on a phenomenon that is omnipresent in the world of membranes, the so-called osmosis. If certain molecules are present in a larger concentration outside the cell than inside the cell – i.e. they form a so-called hypertonic solution – then water will flow out of the cell and the cell will contract.

Nanorods

"We have essentially developed tunable photonic materials whose properties can be manipulated by changing their orientation with external fields," said Yin, an assistant professor of chemistry. "These nanorods with configurable internal periodicity represent the smallest possible photonic structures that can effectively diffract visible light. This work paves the way for fabricating magnetically responsive photonic structures with significantly reduced dimensions so that color manipulation with higher resolution can be realized."


Applications of the technology include high-definition pattern formation, posters, pictures, energy efficient color displays, and devices like traffic signals that routinely use a set of colors. Other applications are in bio- and chemical sensing as well as biomedical labeling and imaging. Color displays that currently cannot be seen easily in sunlight – for example, a laptop screen – will be seen more clearly and brightly on devices that utilize the nanorod technology since the rods simply diffract a color from the visible light incident on them.

Nanoparticles /Nanopowder - Metal, Oxide, Carbide, Nitride, Carbon Nanotube, & Dispersion 

Molecular nanotechnology

Molecular nanotechnology (MNT): a technology based on the ability to build structures to complex, atomic specifications by means of mechanosynthesis.This is distinct from nanoscale materials. Based on Richard Feynman's vision of miniature factories using nanomachines to build complex products (including additional nanomachines), this advanced form of nanotechnology (or molecular manufacturing) would make use of positionally-controlled mechanosynthesis guided by molecular machine systems. MNT would involve combining physical principles demonstrated by chemistry, other nanotechnologies, and the molecular machinery of life with the systems engineering principles found in modern macroscale factories.

Nanotechnology is going to change the world and the way we live, creating new scientific applications that are smaller, faster, stronger, safer and more reliable, including: New Medical Treatments Nanomedicine is focused on diagnosing and treating diseases and creating new drug delivery techniques with fewer side effects. Many nanomedicine findings are now in clinical trials and could soon be available to the public.

• Nanotech-enabled sensors may be able to “smell” cancer. Researchers have mapped the odor profile of certain skin cancers and are looking into ways to create a small electronic nose able to sense the airborne chemical pattern of skin cancer and other odors.

• Gold nanoparticles can be used to detect early stage Alzheimer’s. Other nanostructures can recognize diseased cells and deliver drugs to cancerous tumors without harming healthy cells or organs. Some researchers are designing new nanoparticles to improve biomedical imaging.

• Research is underway to use nanotechnology to engineer a gel that spurs the growth of nerve cells. The gel fills the space between existing cells and encourages new cells to grow. This process could be used to re-grow lost or damaged spinal cord and brain cells.

What is Nanotechnology?

A basic definition: Nanotechnology is the engineering of functional systems at the molecular scale. This covers both current work and concepts that are more advanced.

In its original sense, 'nanotechnology' refers to the projected ability to construct items from the bottom up, using techniques and tools being developed today to make complete, high performance products.

Much of the work being done today that carries the name 'nanotechnology' is not nanotechnology in the original meaning of the word. Nanotechnology, in its traditional sense, means building things from the bottom up, with atomic precision. This theoretical capability was envisioned as early as 1959 by the renowned physicist Richard Feynman.ased on Feynman's vision of miniature factories using nanomachines to build complex products, advanced nanotechnology (sometimes referred to as molecular manufacturing) will make use of positionally-controlled mechanochemistry guided by molecular machine systems.

Photos of Brain

mammals grew dramatically

     The extinction of dinosaurs some 65 million years ago made way for mammals to grow in size – about a thousand times bigger than they had been, a new study has found.

The maximum size of mammals in the post-dinosaur era levelled off about 25 million years later, or 40 million years ago, as the ecosystem was able to reset itself relatively quickly, found the study published in the journal Science.

"Basically, the dinosaurs disappear and all of a sudden there is nobody else eating the vegetation. That's an open food source and mammals start going for it, and it's more efficient to be an herbivore when you're big," said study co-author Dr Jessica Theodor, an associate professor at the University of Calgary in Canada.

"You lose dinosaurs 65 million years ago, and within 25 million years the system is reset to a new maximum for the animals that are there in terms of body size. That's actually a pretty short time frame, geologically speaking," she said.

"That's really rapid evolution."

The researchers spent about three years searching the existing literature and an extensive fossil database for information about the evolution of mammal dimensions.

They found that many types of mammals living all over the world consistently experienced growth spurts followed by a plateau. By developing a model to explain the growth rate, the team discovered that the maximum size levelled off because of ecological constraints, such as the progressive decline in suitable habitats for colossal animals.

According to Theodor, mammals grew from a maximum of about 10 kilogrammes when they were sharing the earth with dinosaurs to a maximum of 17 tonnes afterwards.

"Nobody has ever demonstrated that this pattern is really there. People have talked about it but nobody has ever gone back and done the math," said Theodor, one of the 20 researchers from around the world who worked on the study.

Homology and Homoplasy

Homology means the similarity due to the common ancestor. Homoplasy, on the other hand, means similarity due to convergent evolution, but independent origins. For instance, take the fin and the caudal fin of tuna and of dolphin; they are similar but have independent histories, and their similarity comes from adaptation to similar environments and functions. This is homoplasy. However, the fin of tuna and bonito are similar because of the common ancestor, and that's homology.

To test phylogenetic hypotheses, scientists must be able to find out which similarities indicate a close relationship between species and which do not. The key to this process is determining the evolutionary origins of the similar features. Only similarities inherited from the species' common ancestor can provide evidence of phylogenetic relationship, because they are evidence of a genetic continuity from the common ancestor. Such a similarity, inherited in common form from a single common ancestor, is called homology.

Habitable Zone

Extrasolar planets, or exoplanets for short, have been known to exist outside our solar system since 1995. When searching for life in outer space, scientists focus on those exoplanets that are located in the habitable zone. This means that they orbit their sun at a distance where the temperatures on the planet's surface allow for the presence of liquid water. Water is believed to be an essential ingredient for life. Until now, the two main drivers thought to determine a planet's temperature were the distance to the central star and the composition of the planet's atmosphere. By studying the tides caused by low-mass stars on their potential earth-like companions, Heller and his colleagues have concluded that tidal effects modify the traditional concept of the habitable zone.

Heller deduced this from three different effects. Firstly, tides can cause the axis of a planet`s rotation to become perpendicular to its orbit in just a few million years. In comparison, Earth's axis of rotation is inclined by 23.5 degrees -- an effect which causes our seasons. Owing to this effect, there would be no seasonal variation on such Earth-like planets in the habitable zone of low-mass stars. These planets would have huge temperature differences between their poles, which would be in perpetual deep freeze, and their hot equators which in the long run would evaporate any atmosphere. This temperature difference would cause extreme winds and storms.

The second effect of these tides would be to heat up the exoplanet, similar to the tidal heating of Io, a moon of Jupiter that shows global vulcanism.

Finally, tides can cause the rotational period of the planet (the planet's "day") to synchronize with the orbital period (the planet's "year"). This situation is identical to the Earth-moon setup: the moon only shows Earth one face, the other side being known as "the dark side of the moon." As a result one half of the exoplanet receives extreme radiation from the star while the other half freezes in eternal darkness.

The habitable zone around low-mass stars is therefore not very comfortable -- it may even be uninhabitable. From an observer's point of view, low-mass stars have so far been the most promising candidates for habitable exoplanets. Now, due to Heller's findings, Earth-like exoplanets that have already been found in the conventional habitable zone of low-mass stars, have to be re-examined to consider tidal effects.

Heller and his colleagues have applied their theory to GI581g: an exoplanet candidate that has recently been claimed to be habitable. They find that GI581g should not experience any seasons and that its day is synchronized with its year. There probably would be no water on the planet's surface, rendering it uninhabitable.

Heller said, "I think that the chances for life existing on exoplanets in the traditional habitable zone around low-mass stars are pretty bleak, when considering tidal effects. If you want to find a second Earth, it seems that you need to look for a second Sun."

Host DNA

Interferons (IFNs) are released by mammalian cells upon attack by microbial pathogens, alerting neighboring cells to prepare a defense that includes the activation of so-called IFN-stimulated genes. Although this response nearly always limits viral replication, its role during bacterial infection has not been clear. In some cases, the IFN response accelerates bacteria clearance, but in other cases, it results in a more severe disease (1, 2). The latter is true for Listeria monocytogenes, the bacterium that causes a range of human illnesses, from gastroenteritis to fatal meningitis. On page 1319 of this issue, Lebreton et al. (3) identify a new virulence factor, LntA, secreted by L. monocytogenes, that controls the expression of IFN-stimulated genes. The mechanism allows the bacterium to govern both the induction and repression of the host cell immune response, perhaps to optimize conditions for specific stages of infection or colonization of specific tissues.

DNA Repair Pathways

Direct Reversal The simplest of the human DNA repair pathways involves the direct reversal of the highly mutagenic alkylation lesion O6-methylguanine (O6-mG) by the product of the MGMT gene (O6-methylguanine DNA methyltransferase). The O6-mG adduct is generated in low levels by the reaction of cellular catabolites with the guanine residues in the DNA.

Correction of the lesion occurs by direct transfer of the alkyl group on guanine to a cysteine residue in the active site of MGMT in a "suicide" reaction. The inactivated alkyl-MGMT protein is then degraded in an
ATP-dependent ubiquitin proteolytic pathway.

This energetically expensive repair mechanism for the correction of a relatively simple alkyl-adduct implies O6-mG is extremely detrimental to the cell. Accordingly, a number of chemotherapeutic agents that attack the O6 position of guanine have been developed and are in clinical use.

BER Base excision repair (BER) is a multi-step process that corrects non-bulky damage to bases resulting from oxidation, methylation, deamination, or spontaneous loss of the DNA base itself. These alterations, although simple in nature, are highly mutagenic and therefore represent a significant threat to genome fidelity and stability.

BER has two subpathwaysboth of which are initiated by the action of a DNA glycosylase that cleaves the N-glycosidic bond between the damaged base and the sugar phosphate backbone of the DNA. This cleavage generates an apyrimidinic/apurinic (AP) or abasic site in the DNA. Eight DNA glycosylases with partially overlapping base adduct specificity have been identified in humans. Alternatively, AP sites can also arise by the spontaneous hydrolysis of the N-glycosidic bond. In either case, the AP site is subsequently processed by AP Endonuclease 1 (APE1) which cleaves the phosphodiester backbone immediately 5' to the AP site, resulting in a 3' hydroxyl group and a transient 5' abasic deoxyribose phosphate (dRP). Removal of the dRP can be accomplished by the action of DNA polymerase beta (Pol b), which adds one nucleotide to the 3' end of the nick and removes the dRP moiety via its associated AP lyase activity. The strand nick is finally sealed by a DNA ligase, thus restoring the integrity of the DNA. Replacement of the damaged base with a single new nucleotide as described above is referred to as "short-patch" repair and represents approximately 80-90% of all BER.

DNA Damage

The maintenance of genome integrity and fidelity is essential for the proper function and survival of all organisms. This task is particularly daunting due to constant assault on the DNA by genotoxic agents (both endogenous and exogenous), nucleotide misincorporation during DNA replication, and the intrinsic biochemical instability of the DNA itself.

Failure to repair DNA lesions may result in blockages of transcription and replication, mutagenesis, and/or cellular cytotoxicity.In humans, DNA damage has been shown to be involved in a variety of genetically inherited disorders, in aging,and in carcinogenesis.

All eukaryotic cells have evolved a multifaceted response to counteract the potentially deleterious effects of DNA damage Upon sensing DNA damage or stalls in replication, cell cycle checkpoints are activated to arrest cell cycle progression to allow time for repair before the damage is passed on to daughter cells. In addition to checkpoint activation, the DNA damage response leads to induction of transcriptional programs, enhancement of DNA repair pathways, and when the level of damage is severe, to initiation of apoptosis.All of these processes are carefully coordinated so that the genetic material is faithfully maintained, duplicated, and segregated within the cell.

DNA Structures

 

 

 

Hershey and Chase experiment on DNA

In 1952, Alfred D. Hershey and Martha Chase conducted a series of experiments to determine whether protein or DNA was the hereditary material. By labeling the DNA and protein with different (and mutually exclusive) radioisotopes, they would be able to determine which chemical (DNA or protein) was getting into the bacteria. Such material must be the hereditary material (Griffith's transforming agent). Since DNA contains Phosphorous (P) but no Sulfur (S), they tagged the DNA with radioactive Phosphorous-32. Conversely, protein lacks P but does have S, thus it could be tagged with radioactive Sulfur-35. Hershey and Chase found that the radioactive S remained outside the cell while the radioactive P was found inside the cell, indicating that DNA was the physical carrier of heredity.

 

                                                                                                                                                                                                                                                                                                                                                                                                                             Diagrams illlustrating the Hershey and Chase experiment that supported DNA as the hereditary material while it also showed protein was NOT the hereditary material.

Bacteriophage virus

               In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty revisited Griffith's experiment and concluded the transforming factor was DNA. Their evidence was strong but not totally conclusive. The then-current favorite for the hereditary material was protein; DNA was not considered by many scientists to be a strong candidate.

            The breakthrough in the quest to determine the hereditary material came from the work of Max Delbruck and Salvador Luria in the 1940s. Bacteriophage are a type of virus that attacks bacteria, the viruses that Delbruck and Luria worked with were those attacking Escherichia coli, a bacterium found in human intestines. Bacteriophages consist of protein coats covering DNA. Bacteriophages infect a cell by injecting DNA into the host cell. This viral DNA then "disappears" while taking over the bacterial machinery and beginning to make new virus instead of new bacteria. After 25 minutes the host cell bursts, releasing hundreds of new bacteriophage. Phages have DNA and protein, making them ideal to resolve the nature of the hereditary material.

Molecular Genitics

The physical carrier of inheritance

While the period from the early 1900s to World War II has been considered the "golden age" of genetics, scientists still had not determined that DNA, and not protein, was the hereditary material. However, during this time a great many genetic discoveries were made and the link between genetics and evolution was made.

Friedrich Meischer in 1869 isolated DNA from fish sperm and the pus of open wounds. Since it came from nuclei, Meischer named this new chemical, nuclein. Subsequently the name was changed to nucleic acid and lastly to deoxyribonucleic acid (DNA). Robert Feulgen, in 1914, discovered that fuchsin dye stained DNA. DNA was then found in the nucleus of all eukaryotic cells.

During the 1920s, biochemist P.A. Levene analyzed the components of the DNA molecule. He found it contained four nitrogenous bases: cytosine, thymine, adenine, and guanine; deoxyribose sugar; and a phosphate group. He concluded that the basic unit (nucleotide) was composed of a base attached to a sugar and that the phosphate also attached to the sugar. He (unfortunately) also erroneously concluded that the proportions of bases were equal and that there was a tetranucleotide that was the repeating structure of the molecule. The nucleotide, however, remains as the fundemantal unit (monomer) of the nucleic acid polymer. There are four nucleotides: those with cytosine (C), those with guanine (G), those with adenine (A), and those with thymine (T).


Molecular structure of three nirogenous bases. In this diagram there are three phosphates instead of the single phosphate found in the normal nucleotide.

During the early 1900s, the study of genetics began in earnest: the link between Mendel's work and that of cell biologists resulted in the chromosomal theory of inheritance; Garrod proposed the link between genes and "inborn errors of metabolism"; and the question was formed: what is a gene? The answer came from the study of a deadly infectious disease: pneumonia. During the 1920s Frederick Griffith studied the difference between a disease-causing strain of the pneumonia causing bacteria (Streptococcus peumoniae) and a strain that did not cause pneumonia. The pneumonia-causing strain (the S strain) was surrounded by a capsule. The other strain (the R strain) did not have a capsule and also did not cause pneumonia. Frederick Griffith (1928) was able to induce a nonpathogenic strain of the bacterium Streptococcus pneumoniae to become pathogenic. Griffith referred to a transforming factor that caused the non-pathogenic bacteria to become pathogenic. Griffith injected the different strains of bacteria into mice. The S strain killed the mice; the R strain did not. He further noted that if heat killed S strain was injected into a mouse, it did not cause pneumonia. When he combined heat-killed S with Live R and injected the mixture into a mouse (remember neither alone will kill the mouse) that the mouse developed pneumonia and died. Bacteria recovered from the mouse had a capsule and killed other mice when injected into them!

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AppTitude for Citrix XenApp lets you:
Dramatically reduce application virtualization deployment time and cost
Avoid the risk of isolations causing applications to fail
Identify dependencies early on and enable successful profiling
Identify issues and unsuitable components and reduce failures.

Achieving Application Virtualization

XenApp manages application virtualization by isolating them from one another and from the operating system. That's fine for most applications but could cause problems for those that need to be integrated tightly with the OS, or that rely on other applications to function properly.

AppTitude for XenApp tells  what’s ready for application virtualization, which applications need help and what you can do about any issues. So you can clearly see your estate's XenApp readiness and the resources you'll need to make the transition to application virtualization.

Molecular DNA

DNA (deoxyribonucleic acid), the giant molecule that carries genetic information in living things, is made up of just a few chemical building blocks that bond together in very particular ways.


A typical molecule of DNA consists of two strands that are linked together. A segment can be visualized as a ladder-like structure:

(Actually DNA looks like a twisted ladder or a spiral staircase, a shape commonly called a helix or, since there are two strands in the structure, a double helix. Here we are focusing just on the structure of the ladder.)


In our flat unrealistic model picture we are visualizing the DNA as made of two strands, a left and a right, which are linked in the middle. In reality, since the ladder is twisted, there really is no "right" or "left," but we use that terminology here since it applies to the model graphs. The square shapes and diamonds you see in the middles of the "rungs" are the links, which are meant to represent the different chemical bonds between the two strands of DNA.


Each of the two strands of DNA consists of a sequence of nitrogenous bases, and any one of four such bases can appear on a strand. (The DNA also contains other molecular building blocks like sugars and phosphate groups, but the nitrogenous bases are the genetically important part.) The four bases and our geometric representation of each are as follows:

Base

Representation