What is it about?

Experiments to measure a single molecule/particle, i.e., an individual molecule/particle, at room temperature or under physiological conditions without immobilization—for example, on a surface or without significant hydrodynamic flow—have so far failed. This failure has given impetus to the underlying theory of Brownian molecular motion towards its stochastics due to diffusion. Quantifying the thermodynamic jitter of molecules/particles inspires many and forms the theoretical basis of single-molecule/single-particle biophysics and biochemistry. For the first time, our simulation results for a live cell (cytoplasm) show that the tracks of individual single molecules are localized in Brownian motion, while there is fanning out in fractal diffusion (anomalous diffusion). Keywords: individual molecule tracking; individual molecule; single molecule; diffusion; thermodynamic jitter; live cell; cytoplasm; liquids; room temperature; continuous-time random walk (CTRW); Brownian motion; anomalous motion; computer simulation

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Why is it important?

The formulas and relationships specified in this article apply. They are straightforward and safe for determining how many molecules are averaged during measurement times. They must be used to validate that only a single molecule/a single particle (an individual molecule/an individual particle; the (self)same molecule/the (self)same particle) is measured with high probability during the measurement times. The obtained results are directly linked to the call for increased sensitivity in the time domain of measurements.

Perspectives

The measurement of the individual molecule or particle is one of the most demanding research trends in spectroscopy, microscopy and nanoscopy. This is not least the case because individual molecules (oligonucleotides and single-stranded DNA sequences) were first theoretically described in chemical oligonucleotide syntheses on solid supports after their release from the solid phase as early as 1994 [20], but corresponding measurements are not yet possible today. A head start is the mathematically proven theory that turns knowledge into strength, even at odds with the mediocre mainstream; for example, ref. [21], with additional examples found in ref. [11]. What new insights can be gained from the foundation of the theory on ‘single-molecule/single-particle biophysics and biochemistry based on the stochastic nature of diffusion’, that is, the new physical theory for quantifying the thermodynamic jitter of molecules/particles without immobilization on an artificial surface, on a biological structure or without significant hydrodynamic flow? For example, the thermodynamic signatures of single molecules and single particles in liquids and live cells (cytoplasm, membranes, nucleus) without immobilization or hydrodynamic flow were found in ref. [14] and shown by simulations in Figure 1 and Figure 2 of the present article. There may be too much thermodynamic jitter in the experiments with live cells and diluted liquids without immobilization or significant hydrodynamic flow under physiological conditions or at room temperature [22]. Taken together, this article presents a significant advancement in single-molecule/particle biophysics and biochemistry through simulations demonstrating localized Brownian motion and fractal diffusion. The introduction and methods sections provide a thorough background and detailed methodology. Of course, there are many types of live cells. The study does not differentiate between them, but this could be achieved by using more specific values for underlying fractal structures and distribution functions.

PRESERVE FROM BEING FORGOTTEN: Professor Zeno Földes-Papp [Biochemist, Gerontologist (Biochemiker, Geriater)]: Laying the Foundation of Single-Molecule Biophysics & Biochemistry Based On the Stochastic Nature of Diffusion: The Individual Molecule, from the Mathematical Core to the Physical Theory. -- I hope that my humble scientific work will be well received by the communities of single-molecule imaging and spectroscopy and by all users of these technologies as well as biotechnologies in the various and different disciplines:
Head of Geriatric Medicine (Medical Director of the Geriatric Service: Sektionsleitung Geriatrie) at Asklepios Klinikum Lindau (Bodensee), Bavaria, Germany

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This page is a summary of: Single-Molecule Tracking in Live Cell without Immobilization or without Hydrodynamic Flow by Simulations: Thermodynamic Jitter, Biophysica, August 2024, MDPI AG,
DOI: 10.3390/biophysica4030028.
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