26 Dec 2011

Molecular Machines Gallery

Beware of the stroboscopic illusion!!

If molecular models really moved while revealed in the animations underneath, that they couldn't work. Do not pin the consequence on your simulation or perhaps the look, though. The issue is the regular way to render video clip support frames makes a stroboscopic impression regarding jerky movement. Atoms generally vibrate countless times for each body, yet regular frames catch the positioning of each and every atom with a one quick, just as if noticed with the display of your stroboscope. That creates the actual optical illusion which the atoms most vibrate at the shape charge, that is too towards the regularity in the machine's transferring components. This provides you with this misconception how the device parts are going on just about arctic pace, just like this pace associated with appear. From that will pace, even though your machine proved helpful, chaffing would be intolerable.

MarkIII(k) Planetary Gear
Here is the MarkIII(e ), some sort of nanoscale planetary equipment created by K. Eric Drexler. A planetary gear couples a good input canal via a sun tools with an result the whole length as a result of a collection of earth things (attached with the actual end result the whole length by way of a planet service ). Our world things throw between the sun tools and also a band items for the internal surface of a casing. This particular toon seemed to be made along with Qutemol by means of reading through PDB documents from your NanoEngineer-1 molecular mechanics simulation. THE part of the actual ouert shell atoms are actually invisible to help promote the interior gearing set up..,

Nanorex, Inc.



And here is your SRG-Ic, virtually any parallel-shaft swiftness reducer merchandise put together by Quantities Sims. This been found designed and in addition simulated thoroughly applying NanoEngineer-1. This specific assemblage ıs known for a pinion physical objects, some form of effect objects, as well as a silicon carbide defending having a number of utilized bushings (accessibility means along with rear). Concerning in which SRG-I may be to create a uncomplicated price reducer products put together with simply because quantity of atoms since they may be.

Mark Sims
Nanorex, Inc.


This is the SRG-II. It had been patterned besides simulated just making use of NanoEngineer-1 (Alpha dog 6). The goal of the actual SRG-II appeared becoming to produce a effective nanoscale items which includes any kind of property along with long connection shafts. That you could see, the specific SRG-II presents itself only like a swiftness reducer goods.

Mark Sims
Nanorex, Inc.


This is sometimes a SRG-III. That been found modeled plus simulated entirely implementing NanoEngineer-1. A brand new crossbreed while using SRG-I together with SRG-II, oahu is the 2nd molecular items coach previously meant. Acquiring 15, 342 atoms, your SRG-III will be the upcoming biggest nanomechanical system really patterned inside atomic aspect.

Mark Sims
Nanorex, Inc.


NanoEngineer-1 Gallery: SRG-III Speed Reducer Gear

Designer: Mark Sims
Time: AUG 31, 2005
Amount of parts: 4
Quantity of atoms: 15,342
Size: 11.3 nm
Peak: 7.5 nm
Interesting depth: 5. 6 nm
Gear Ratio: 13: 6
Speed Ratio: 2. 167: 1

This SRG-III could possibly be the ultimately parallel-shaft velocity reducer items put together by Marking Sims. Any cross from the SRG-I in conjunction with SRG-II, could it be does not very first molecular items prepare basically intended. Applying 15, 342 atoms, the SRG-III would be the minute finest nanomechanical gadget in the past patterned within atomic detail.

This kind of movements connect exhibits a portion in the molecular character simulation during which had obtained almost thirty-one a while to try and do along with my personal Dell laptop computer. We now have taken out the exact front-top 1 or two this particular silicon carbide outer shell that you can explose the equipment educate.
The exact rotary generator (certainly not verified) is often that come with the top items possesses the following factors:
Torque: 10 nN-nm
First rate: 0 GHz
Supreme Speed: 100 GHz
As i used another issues with this simulation:
Casings: 1100
Measures for each design: 100
Heat selection: 3 hundred

This anime never-ending cycle displays your own housing shown using hoses mode.
- Mark

NanoEngineer-1 Gallery: SRG-I Speed Reducer Gear

Name: SRG-Ia
Designer: Mark Sims
Time: AUG 27, 2005
Amount of parts: four
Quantity of atoms: 2, 924
Size: 4. 7 nm
Peak: 2. 8 nm
Interesting depth: 3. 6 nm
Gear Ratio: 3: 2
Speed Ratio: 1. 5: 1.

This is the particular SRG-Ia, any parallel-shaft speed reducer merchandise assembled by Tag Sims. That you can see, it offers 5 materials: a good type in base, a output canal plus some paired bushings (front door as well as raise). Depending on actual SRG-Ia found themselves getting to make a standard pace reducer solutions getting considering that variety of atoms as it can be.
Small opinions apparatus along with bushing may very well be identifiable for your requirements. There're credited via Drexler's Very little Displaying, which includes gotten ones canal substantial as well as one more burn for the having that include concluding. The exact sulfur atoms regarding the outside from the modest showing foundation in which transmuted so that you can silicon, which allows further sections connected with atoms for being added to help formulate and as well create series associated with steric enameled.

That mix component of this particular enter in addition to end result equipment absolutely demonstrates the way in which it ended up achieved. Know that even though 6-fold evenness seemed to be cared for inside enter in products, the quantity of tooth was bending by six so that you can endless weeks of frustration.

Such as strategies goods, the harder high priced generation tools is normally some form of type from the little demonstrating. Within your channel, oxygen atoms appeared place between intrinsic many carbons to further improve your radius. In contrast to the tips items, the degree from the enamel wouldn't twin as clleular layers concerning atoms wound up involved. When you rely the number of air flow atoms (during red-colored) combined with the amount of teeth enamel, they each the exact same of sixteen.

This type of POV-Ray generating suggests top in addition to backed bushings throughout Pipe joints demonstrate mode, allowing you to be aware of the aspect concerning equally factors typically obscured from the bushings. You can even find out the particular several sulfur atoms used to help get together the 2 bushings. Realize that in the super-hero regime below, these kinds of atoms tend not to proceed. The reason being controversy were being placed on them all, anchoring these kind of within the simulation.

The 2 of the super-hero artwork show the leading rewarding simulation with the SRG-Ia. Them required 30 a long time to complete with a Pentium 4 CPU @ 2 GHz possessing 512 MB. This kind of guidelines was applied:
Borders: 5000
Steps for every single structure: 500 (50 femtoseconds)
Temperature ranges: 300K
This specific simulation lit up any design and style concern with this end result items, which could be noticed in that toon never-ending never-ending loop before. When you glimpse thoroughly, you will see breathable oxygen atoms inside boundary on the merchandise stovetop popcorn accessible intermittenly. That's characteristic that this t-mobile atoms usually are compressed too snugly through this the complete duration. When i required to address that matter in some way.
My partner and i additionally constructed a couple of faults inside simulation construct. My spouse and i essential which will location your electrical engine for that perception channel, however Once i linked an item about the result canal somewhat. That is noticeable around the mobility line: place the actual understanding the whole time-span rattling all-around inside bushing although productivity the complete duration transforms more efficiently. The actual assortment of atoms in order to spine had not been nicely thought to be, equally.

SRG-Ia (8/31/2005)

Using this type of present simulation from your SRG-Ia, that insight tools offers the rotary electric powered motor and it's also working the actual effect objects. The actual anchors are actually strategically place through areas that any of us predict will surely connect with the SiC protecting (on the other hand for being intended). Realize that this kind of sulfur atoms coupling both bushings of which provide points aren't anchored, a new smart scenerio.
Seemingly because of this simulation the actual big bushing needs to have a smaller radius. You can unsurprisingly go to a distinction involving the end result channel and also the bushing from the animiation, which often just isn't surprising since i have didn't meticulously review that atomic miles concerning canal as well as bushing that range the particular demonstrating.

To ensure the long term employment have been in order to spot light refining your efficiency resources. I was needed to handle a number of issues:

Slow up the level of series relating to breathable fresh air atoms in the particular base.
Lower how big is your bushing with the far better go with about the canal.
SRG-Ib (9/2/2005)

This is actually the SRG-IIb, which in turn handle each issues When i identified mentioned before. Once i moreover bundled your silicon carbide (SiC) covering to allow the things, offering a full getting your current device in concert technique having 8, 366 atoms. Up to date goods along with bushing mix is much far more hard to stick to, creating simple revolving on the inside bushings.
From the simulation variety inside the acceptable, The partner and when i thought i would include things like simply this particular equipment along with atoms through your bushings, as well as a a number of atoms that connect your current bushings on the spanning. This aided the specific simulation to try and do more quickly although however secure protecting the specific atoms which produce the key performance with the system.

With this brand-new mixture a part of that apparatus, you will observe generate profits decreased the degree of o2 atoms for the medial aspect the specific productivity items the entire time-span. That brought about any a bit small the full size sizing, demanding further modifications for that bushing.

Through this POV-Ray thing object rendering, you'll be able to surely check out the particular atoms with all the current black coloration wireframe bins which are grounded using the simulation, which might be people atoms that get connected to nearby external layer atoms (taken away with the simulation). You can also start to see the genuine base on the rotary power generator working the suggestions (pinion) items in the simulation.
SRG-Ic (9/4/2005)

This kind of simulation while using SRG-Ic contains most atoms, also individuals on the inside brand-new housing. The exact SRG-Ic varies throughout the SRG-Ib merely on the addressing style. My partner and i pruned atoms on the attributes on the Ib that i sensed ended up being unneeded. These kinds of lowered ones atom make any difference via 8, 366 for you to 7, 704.
In regards to the quit, this spanning might be displayed on the inside Pontoons fashion when you go the armor in addition to tool enhancements are already still left during CPK perform. This arrangement enables almost all atoms inside of spanning currently being exhibited without the need of obsuring the specific character with all the factors. Inside POV-Ray movement from the appropriate, We have recinded the perfect 1 and only two of foremost houses in order to reveal the exact factors.
- Mark

NanoEngineer-1 Gallery: MarkIII(ok) Planetary Stuffs

Identify: MarkIII(k)
Developer: K. Eric Drexler
Time frame: 2004
Number of ingredients: 12
Quantity of atoms: 3, 853
Width: 4.2nm
Top: 4.2 nm
Degree: 4.2 nm
Gear Ration: 45: 16
Swiftness Relation: 2. 8125: 1
Output Torque: > 1x10-18 m-N
Angular Pace > 10 GHz
Energy > 1 nW
Strength Occurrence>10 GW/cm2
Performance > 99. 8%.
 This is often a MarkIII(alright), a new planetary gear constructed simply by Alright. Eric Drexler. Virtually any planetary methods lovers the actual strategies base by using a photo voltaic resources for an production shaft with a collection of world things (installed on this kind of result the whole length by using a world services). The earth items swivel between your sunshine products and also a diamond ring equipment about the on the inside external in the outside covering. Your toon down below was produced from the particular NanoEngineer-1 molecular figure simulation. An integral part of the particular real estate atoms happen to be concealed to be able to present the interior gearing set up.
Planetary gears are generally interesting locates intended for molecular modeling due to the fact (in addition to careful collection of globe numbers besides sun- in conjunction with ring-gear symmetries) your evenness with all the program fundamentally ensures lessened vitality restrictions over the needed moves put together. Also, they will lot sizeable complication right into a small design and style.
Planetary issues usually are standard physical strategies a good choice for speed decreasing (= torque multiplication). Macroscale versions are found inside automobile transmissions, electric powered screwdrivers, along with Mars landers.
This kind of MarkIII(acceptable) items mail messages an early on 1990s style through Drexler besides Merkle, changed to scale back relationships involving the sun merchandise as well as the facets from everyone tools. The original kind were being beautifully made with little transferring elements so as to go with this computational demands of times. Planet earth gears usually are within the decrease restrictions associated with top relating to well-designed resources materials, besides because of this, the "gear teeth" through this process tend to be higher considered to be fresh, low-amplitude corrugations in the items floor surfaces.

Your individual covalent (sigma) provides backlinks every one of the several world gears for the company objects are easily seen in this excellent POV-Ray picture.

25 Dec 2011

Joint CSIR UGC NET Exam Result December 2011 Exam Paper Answers | 26-12-2011

Joint CSIR UGC NET Exam Result December 2011 Exam Paper  Answers

1 -1 , 2-2, 3-4, 4-4, 5-4, 6-1 , 7 -3, 8-3, 9-1 , 1 0-4, 1 1 -4, 1 2-1 , 1 3-1 , 1 4-3, 1 5-4, 1 6-4, 1 7 -2, 1 8-1 ,
1 9-2, 20-1 .

21 -4, 22-1 , 23-2, 24-1 , 25-4, 26-2, 27 -3, 28-3, 29-4, 30-2, 31 -2, 32-1 , 33-4, 34-1 , 35-2, 36-1 ,37 -2, 38-3, 39-1 , 40-4, 41 -1 , 42-1 , 43-2, 44-2, 45-2, 46-4, 47 -4, 48-2, 49-3, 50-4, 51-4, 52-2,53-1 , 54-2, 55-2, 56-4, 57 -4, 58-4, 59-1 , 60-1 , 61 -3, 62-2, 63-2, 64-4, 65-2, 66-2, 67 -1 , 68-,69-2, 7 0-2.

7 1 -2, 7 2-4, 7 3-4, 7 4-3, 7 5-3, 7 6-1 , 7 7 -2, 7 8-3, 7 9-2, 80-4, 81 - may be 2, 82-2, 83-2, 84-1 , 85-1 , 86-1 , 87 -2, 88-4, 89-2, 90-3, 91 -1 , 92-3, 93-1 , 94-3, 95-2, 96-4, 97 -1 , 98-3, 99-3, 1 00-1 ,101 -3, 1 02-2, 1 03-1 , 1 04-4, 1 05-2, 1 06-, 1 07 -1 , 1 08-1 , 1 09-1 , 1 1 0-2, 1 1 1 -3, 1 1 2-3, 1 1 3-3, 1 1 4-1 , 1 1 5-2, 1 1 6-3, 1 1 7 -2, 1 1 8-1 , 1 1 9-2, 120-2, 121 -1 , 122-2, 123-2, 124-1 , 125-1 , 126-4, 127 -2,128-3, 129-, 130-3, 131 -1 , 132-4, 133-1 , 134-3, 135-3, 136-3, 137 -2 or 3, 138-2, 139-1 , 140-3, 141 -3, 142-may be 2, 143-1 , 144-1 , 145-.

Joint CSIR UGC NET Exam Result

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23 Dec 2011

Nanotechnology | Nanotechnology coatings

What on earth is Nanotechnology?
A simple definition: Nanotechnology is the executive regarding functional programs at the molecular level. This insures both present works in addition to ideas which can be heightened.
Throughout its initial perception, 'nanotechnology' means the actual projected chance to construct things on the bottom up, employing strategies in addition to instruments currently being developed nowadays to produce total, top rated goods.

The meaning of Nanotechnology

When K. Eric Drexler (correct ) popularized the saying 'nanotechnology' from the 1980's, this individual was dealing with making devices within the size regarding compounds, a couple of nanometers wide-motors, trading program biceps and triceps, and in many cases full pcs, considerably small over a cell phone. Drexler put in the next ten years talking about along with studying these kind of amazing gadgets, and answering accusations of science fiction. In the meantime, tedious technological innovation was building the chance to develop straightforward houses on the molecular degree. While nanotechnology evolved into a recognized strategy, the meaning from the concept altered to cover the particular less difficult kinds of nanometer-scale technologies. The particular U. S. National Nanotechnology Initiative is made to advance this sort of nanotech: Their classification incorporates something more compact in comparison with 100 nanometers along with novel components.

Much of the job staying accomplished nowadays of which holds this title 'nanotechnology' is just not nanotechnology within the initial meaning of the word. Nanotechnology, with its regular feeling, suggests developing points in the base upwards, along with atomic perfection. This specific theoretical capacity ended up being created as soon as 1959 through the famous physicist Rich Feynman. 

 “I want to build a billion tiny factories, models of each other, which are manufacturing simultaneously. . . The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big. - Richard Feynman, Nobel Prize winner in physics”

According to Feynman's imaginative and prescient vision of miniature producers utilizing nanomachines to create difficult merchandise, innovative nanotechnology (at times termed as molecular producing) will make full use of positionally-controlled mechanochemistry led by molecular machine devices. Formulating any roadmap for development regarding these kinds of nanotechnology has become an objective of a largely based technological know-how roadmap task brought through Battelle (this supervisor connected with numerous You. Ohydrates. Country wide Laboratories) as well as the Foresight Nanotech Institute.

Shortly after this particular envisioned molecular equipment is created, the item will result in a new creation innovation, likely creating critical trouble. Additionally, it offers severe monetary, social, ecological, in addition to army significance.

See more:- Nanotechnology

Nanotechnology coatings

Four Generations
Mihail (Scott ) Roco from the U. S. National Nanotechnology Initiative possesses explained some ages involving nanotechnology advancement (notice chart underneath ). The latest time, while Roco represents it, will be in which regarding passive nanostructures, resources designed to conduct 1 process. Your second period, which in turn were simply entering, features productive nanostructures regarding multitasking; by way of example, actuators, pill shipping and delivery units, and receptors. Another generation will be required to start promising all-around 2010 and definately will attribute nanosystems along with many bonding elements. Quite a while and then, the primary included nanosystems, operating (according to Roco) a lot like a mammalian cell phone having hierarchical systems within techniques, are expected to be formulated.

Several experts may well nevertheless demand that nanotechnology may reference measurement or visualization with the range connected with 1-100 nanometers, although the opinion looks like it's forming about the idea (put forward by the NNI's Paul Roco) that will control along with restructuring involving issue in the nanoscale is usually a necessary factor. CRN's classification is usually a bit more correct compared to in which, however while function progresses over the four decades of nanotechnology before molecular nanosystems, that may incorporate molecular making, most of us consider it will eventually turn into increasingly obvious which "engineering involving practical methods on the molecular scale" is precisely what nanotech is actually information about.

Disagreeing Meanings

Regrettably, inconsistant definitions regarding nanotechnology and also fuzzy disparities concerning drastically various areas include complicated the effort to understand the particular differences and also acquire practical, effective insurance policy.

The particular pitfalls regarding current nanoscale technologies (nanoparticle toxicity, and so forth. ) can not be handled the same as your dangers associated with longer-term molecular producing (financial trouble, unstable biceps and triceps ethnic background, and so on. ). This can be a error that will put these jointly in one basket with regard to coverage consideration-each is vital to cope with, nonetheless they offer different difficulties all of which will need different alternatives. While utilized nowadays, the definition of nanotechnology usually identifies an easy bunch of generally turned off grounds. Essentially, whatever enough small and exciting is usually known as nanotechnology. Most of it can be harmless. For the relax, a lot of the particular harm is actually of familiar and also restricted quality. Although as we will see, molecular production provides different risks and brand new lessons involving troubles.

General-Purpose Technology

Nanotechnology is oftentimes often called any general-purpose technologies. Which is since in their innovative kind it'll have considerable affect almost all industries and every area connected with modern society. It's going to provide greater created, are more durable, solution, less dangerous, in addition to cleverer goods with the home, regarding marketing and sales communications, with regard to treatments, intended for travelling, intended for farming, and intended for market generally speaking.
Imagine a medical device that travels through the human body to seek out and destroy small clusters of cancerous cells before they can spread. Or a box no larger than a sugar cube that contains the entire contents of the Library of Congress. Or materials much lighter than steel that possess ten times as much strength. - U.S. National Science Foundation

Dual-Use Technology

Similar to power or even computer systems just before that, nanotech offer significantly much better productivity in nearly all facet of life. Although being a general-purpose technological know-how, it'll be dual-use, meaning it's going to have numerous commercial employs and it also may have many military services uses-making a lot more highly effective items and equipment involving security. So this presents besides wonderful benefits pertaining to the human race, but also burial plot risks.

A vital understanding of nanotechnology is actually which it provides besides much better goods, however some sort of enormously improved upon manufacturing process. Your working computer will make reports of files files-essentially several illegal copies because you wish from little or no expense. It can be only a issue of your time prior to the building regarding solutions turns into because affordable as the duplicating involving data files. That is the real significance connected with nanotechnology, as well as the reason why it really is from time to time known as "the future business wave. Inches.
    My own judgment is that the nanotechnology revolution has the potential to change America on a scale equal to, if not greater than, the computer revolution. - U.S. Senator Ron Wyden (D-Ore.)
The ability involving nanotechnology can be encapsulated within an evidently simple device termed your own nanofactory that may lay on your current counter top or perhaps pc. Filled with miniature element processors, research, and robotics, it will eventually develop a wide-range associated with things speedily, cleanly, in addition to low-priced, developing items straight coming from construction plans.
Video Nanotechnology  Click to enlarge

Exponential Growth

Nanotechnology not just enables doing numerous high-quality merchandise from small cost, but it will allow generating brand new nanofactories at the similar cheap along with in the exact same swift velocity. This phenomenal (outside of the field of biology, that is) ability to replicate a means of creation is why nanotech is usually considered to be a rapid technology. It represents a production system which should be able to create much more making systems-factories which could assemble factories-rapidly, inexpensively, in addition to cleanly. Your way of creation should be able to replicate on an ongoing basis, so throughout only a few days a couple of nanofactories certainly may turn into millions. It is a progressive, transformative

Just how soon will more or less everything happen? Conservative quotes generally state 20 in order to 40 many years from currently, or even significantly later on as compared to in which. Even so, CRN can be involved it may perhaps come about quicker, potentially over the following decade. This is because on the rapid progress getting made in enabling systems, for instance optics, nanolithography, mechanochemistry along with 3d prototyping. In case it lets you do appear in which before long, many of us might not be effectively organized, as well as the implications may be severe.

All of us imagine it is not too soon to begin asking several rough queries as well as dealing with the problems:
  •                   Who will own the technology?
  •             Will it be heavily restricted, or widely available?
  •             What will it do to the gap between rich and poor?
  •             How can dangerous weapons be controlled, and perilous arms races be prevented?  

Many of these questions were firstly raised finished a decade since, and control not yet been answered. If the questions are not answered with deliberation, answers will evolve independently and will take us by blow; the blow is likely to be foul.

It is challenging to say in support of certainly how soon this expertise will mature, partly as it's workable (especially in countries with the purpose of figure out not control exposed societies) with the purpose of furtive forces or business development programs control been available on in support of years with no our intelligence.

We cannot say with certainty with the purpose of full-scale nanotechnology will not be industrial with the after that ten years, or even five years. It possibly will take longer than with the purpose of, but prudence—and perhaps our survival—demands with the purpose of we coach without hesitation in support of the most basic plausible development scenario.

 More Background on Nanotechnology:

Productive Nanosystems (From molecules to superproducts)

Visualizing productive nanosystems and molecular manufacturing is a major challenge in communicating the power of this technology. To help address this problem, Nanorex (http://www.Nanorex.Com ) and the Foresight Institute (http://www.Foresight.Org/ ) established a challenge grant to fund the production of a new computer-generated animated short film called "Productive Nanosystems: From Molecules to Superproducts". This was a collaborative project of animator and engineer, John Burch (http://www.Lizardfire.Com/ ), and pioneer nanotechnologist, Dr. K. Eric Drexler (http://www.E-drexler.Com/ ). The film depicts an animated view of a nanofactory and demonstrates key steps in a process that converts simple molecules into a billion-CPU laptop computer

22 Dec 2011

Molecular motors - a lesson in nanotechnology from Nature

Roop Mallik

They are small, and there are billions of them inside you. Tiny machines, a thousandth of the thickness of human hair, but robust and designed for an amazing variety of functions. Science fiction? Think again … this is real, as real as flesh and blood !! If you can get your hands on a high school biology text book, flip through to the mandatory schematic of an animal cell. Look closely, what you will see is not a floppy bag with random things thrown in here and there. There is amazing structural organization within the cell, with several compartments (e.G. The nucleus, Golgi bodies, mitochondria) at specific locations. Many of these compartments are specialized “factories”, each with its own assembly line which requires specific raw material as input and generates specific products. A constant give-and-take of materials occurs within these factories, because each is dependent on the other. In the big picture of things this incessant exchange of material keeps the factories of the cell functioning, which in turn is what keeps us alive.

How do things get moved inside the cell?
Simplified schematic of the transport network of a typical cell. Molecular motors are shown ferrying different cargo. The Kinesin motors usually move towards the cell periphery, while Dyneins move towards the cell center. More detailed schematics of the motors shows the “legs” on which these motors walk while carrying cargo. For an idea of the size scales involved, kinesin and dynein motors have dimensions of approximately 50 nanometers. A nanometer is one-billionth of a meter (10-9 meters). These motors exert forces of pico-Newtons. A pico-Newton is one-thousand-billionth of a Newton (10-12 Newtons). We usually measure forces in Newtons in day-to-day life. “
See more:-Roop Mallik Lab

Molecular motor

Molecular motors

Opposing teams of molecular motors (Dyneins in orange; Kinesin in green) transporting their cargo (ellipsoidal) on a microtubule (Blue tube-like filament at bottom). A lens focusses laser light to trap the cargo and measure force applied by motors

Molecular motors, a lesson in nanotechnology from Nature

The living cell has amazing structural organization. At a first level, this is obvious from the many distinct sub-cellular compartments at specific locations within every tiny cell (e.G. The nucleus, Golgi, mitochondria). Many of these compartments are specialized factories, each with its own assembly line requiring specific raw material as input and generating specific products. A constant give-and-take of materials occurs between these factories inside the cell, because each factory is dependent on the other to function. In the big picture of things this incessant exchange of material keeps the factories of the cell functioning, which in turn is what keeps us alive.

This flow of material occurs in a highly regulated and disciplined manner, so that the right things are present at the right place and time. How does this transport of materials take place? This is where the army of tiny machines called molecular motors comes in. The cell has a network of roadways (one kind of roadways are called microtubules, see Figure) with heavy traffic of molecular motors on them. These motors can be thought of as porters ferrying all kinds of material within the cell. You will be surprised at how well this analogy of molecular motors with porters works, but dont forget that these motors are a 10-million times scaled down version of what your idea of a porter is.

So, what exactly is this motor that works on a molecular scale? One example is a protein with two legs walking along on the cellular roadway, stepping just like a porter and carrying some cellular material as cargo. During every step that the motor takes, it has to generate force and therefore does some work. The energy required for this comes from chewing up a molecule called ATP, which has energy stored in its chemical bonds. For every step that the molecular porter takes, it needs one little packet of energy in the form of an ATP molecule. So, if you travel inside the cell and need somebody to carry your bags, make sure you give them a constant supply of ATP. Just three meals a day does not work at the molecular scale.

Kinesin, one of the best studied molecular motors walks with precise steps of 8 nanometers. For each step, kinesin uses one molecule of ATP and generates 6 piconewtons of force. A simple calculation shows that this makes kinesin a nano-machine with almost 50% efficiency, which is comparable to many machines of human design. To give you an idea of the magnitude of scales here, if a kinesin motor walked upwards starting at your toenail, it would take about 100 million steps to reach your nose. Approximately 1 million-million kinesins would have to team up together to arm-wrestle with you and have any hope of winning. We are really talking nanotech here.

For anyone impressed with kinesin, there is more to come. Dynein is a second class of motors ferrying cargo within the cell, and is much more complicated than kinesin. There is recent evidence that nature has implemented a nanoscale gear mechanism within this complexity. It appears that dynein normally walks with a step size about thrice the size of kinesin. However, if you pull dynein backward the motor can shorten its stepsize and resultantly produce more force, which is just like shifting gears in your car on an uphill road. Only future research can tell why nature felt the need to implement such complex architecture at these minute size scales.

There are many other classes of motors which I have not discussed here for reasons of space, and also to keep the discussion simple. One common theme that has emerged from years of research is that of surprisingly intricate and robust architecture within these molecular motors at a size scale which we are only now beginning to comprehend. It is these little things in life that matter, so let us congratulate nature on a little job very well done !!

Further References