Navigation Links
Glowing beacons reveal hidden order in dynamical systems
Date:10/19/2011

The so-called ergodic theorem formulates a fundamental physical principle relating to the behavior of dynamical systems. Essentially the theorem states that in a multiparticle system each individual particle behaves just as "chaotically" as does the system as a whole. In other words, one can extrapolate from the behavior of a single element to that of the whole system. Strangely enough, in spite of its wide-ranging implications, the theorem has not been rigorously tested experimentally. A collaborative effort mounted by Professor Christoph Bruchle's team in the Department of Chemistry at LMU Munich and Professor Jrg Krger's group at Leipzig University has now confirmed the validity of the theorem by measuring the diffusive behavior of ensembles of particles and the trajectories of single molecules in the same system. Using fluorescent molecules as tracers and high-resolution imaging methods, the LMU investigators were able to track the paths of individual molecules, while the Leipzig group studied the collective behavior of the whole ensemble. "It will be very interesting to take a closer look at systems that do not conform to the tenets of the ergodic theorem and to determine the reasons for their aberrant behavior," says Bruchle.

The term "diffusion" refers to the random motion of particles, such as atoms and molecules, under the influence of thermal energy. This physical process is an essential component of innumerable phenomena in nature, and also plays a crucial role in many technological procedures. For instance, in virtually all chemical reactions, diffusion is responsible for bringing reactants sufficiently close together to enable them to react at all. It is generally accepted that the ergodic theorem is applicable to the dynamics of diffusive processes. The theory basically states that repeated measurements of a given variable such as the distance covered by a particle in a given time interval should yield the same average value as a single measurement of the same variable on a collection of particles provided the system considered is in a state of equilibrium. However, as Krger points out, "although diffusive processes have been investigated for the past 150 years, the principle of ergodicity has not yet been experimentally verified." This is because it has so far been possible to quantify diffusive processes only by means of ensemble measurements i.e. measurements of many particles simultaneously. One of the most informative methods for this purpose is pulsed-field gradient nuclear magnetic resonance (PFG-NMR), a technique for which Krger and his group are well known. The actual trajectory of a single particle, on the other hand, could not be observed directly. "With the development of single-molecule spectroscopy and single-molecule microscopy, we can now follow the trajectories and therefore monitor the diffusion behavior of single molecules," Bruchle explains. Optical tracking methods visualize molecules on the basis of their fluorescence, making it possible for their positions to be localized and monitored with a precision of a few nanometers.

This still leaves one problem to be solved - successful application of the two methods requires very different, indeed apparently conflicting, conditions. NMR measurements need high concentrations of molecules with large diffusion coefficients, while single-molecule spectroscopy works best with extremely dilute solutions of species with small diffusion coefficients. By using particular organic dyes with high fluorescence yields in combination with porous silicate glasses containing networks of nanometer-sized channels in which the dye molecules can diffuse, the researchers were able to create conditions that were compatible with both methods. This experimental set-up allowed them to perform single-molecule and ensemble measurements on the same system.

When the two teams compared their data, they found that the diffusion coefficients (the parameter that describes diffusive motion) obtained by the two techniques agreed with each other providing the first experimental confirmation of the ergodic theorem in this context. The next step will be to examine systems in which the theory does not apply. "The diffusion of nanoparticles in cells looks like an interesting example," says Bruchle, "and for us the important thing is to find out why the ergodic theorem doesn't hold in this case."

The project in Munich was carried out under the support of the Cluster of Excellence "Nanosystems Initiative Munich" (NIM) and DFG Priority Program 749 (Dynamics and Intermediate Molecular Transformations), while the work in Leipzig was supported by the DFG as part of Research Unit 877 (From Local Constraints to Macroscopic Transport). (gd)


'/>"/>

Contact: Dr. Kathrin Bilgeri
kathrin.bilgeri@lmu.de
49-892-180-6938
Ludwig-Maximilians-Universitt Mnchen
Source:Eurekalert

Related biology news :

1. Glowing hands in the waiting room improves kids handwashing
2. TF beacons may light path to new cancer tests and drugs
3. Researchers use nanoparticles as destructive beacons to zap tumors
4. From tropics to poles: Study reveals diversity of life in soils
5. Genetic study of cave millipedes reveals isolated populations and ancient divergence between species
6. Genomic sequence and comparison of 2 macaques reveal new insights into biomedical research
7. Study reveals new role for RNA interference during chromosomal replication
8. Contamination of UK mobile phones and hands revealed
9. Tiny fossil fragment reveals giant-but-ugly-truth
10. Australias endangered bettong reveals how weather effects species distribution
11. University of California Santa Barbara study reveals how gas, temperature controlled bacterial response to Deepwater Horizon spill
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/28/2016)... SYNA ), a leading developer of human interface solutions, today ... --> --> Net revenue ... to the comparable quarter last year to $470.5 million. Net income ... $0.93 per diluted share. --> ... 2016 grew 9 percent over the prior year period to $60.3 ...
(Date:1/22/2016)... January 22, 2016 ... addition of the  "Global Behavioral Biometric ... --> http://www.researchandmarkets.com/research/4lmf2s/global_behavioral ) has ... Behavioral Biometric Market 2016-2020"  report to ... and Markets ( http://www.researchandmarkets.com/research/4lmf2s/global_behavioral ) has announced ...
(Date:1/20/2016)... , Jan. 20, 2016   MedNet Solutions , ... entire spectrum of clinical research, is pleased to announce ... significant achievements are the result of the company,s laser ... iMedNet eClinical , it,s comprehensive, easy-to-use and highly ... --> Key MedNet growth achievements in 2015 ...
Breaking Biology News(10 mins):
(Date:2/8/2016)... R&D program for the development of future natural products for ... research and development center in Israel ... Stockton has a variety of products adapted ... active in more than 35 counties worldwide. ... flagship product Timorex Gold ® is used to control ...
(Date:2/5/2016)... Feb. 5, 2016 ATCC, the premier global ... assist the medical and life science researchers that are ... infection.   CDC website . ... Zika virus is a single-stranded RNA virus of the ... Nile, Dengue and Chikungunya Viruses. Zika virus is transmitted ...
(Date:2/4/2016)... CA (PRWEB) , ... February 04, 2016 , ... ... enterprise talent development and compliance training, today announced an interactive FDA compliance ... Playbook™. The RAPS (Regulatory Affairs Professional Society) accredited interactive course on Morf ...
(Date:2/4/2016)... -- Beike Biotechnology, the Shenzhen ... in late 2015 to mark their successful combined efforts ... --> --> The signing, ... Therapy" was hosted by the Shenzhen Cell Bank and ... Beike Biotechnology Co., Ltd. Shenzhen,s ...
Breaking Biology Technology: