Tapping mode atomic force microscopy in liquids

Hansma, Paul K.; Cleveland, J. P.; Radmacher, Manfred; Walters, D. A.; Hillner, P. E.; Bezanilla, Magdalena; Fritz, Monika; Vie, D.; Hansma, Helen G.; Prater, C. B.; Massié, J.; Fukunaga, L E; Gurley, John; Elings, Virgil B.

doi:10.1063/1.111795

Cited by 824 publications

(435 citation statements)

References 19 publications

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“…Problems arising from unfavorable probe-surface interactions have been obviated to some extent by the development of ''tapping'' mode instruments (Hansma et al, 1994). With tapping mode, the probe tip is not in continuous contact with the sample but oscillates up and down as it is scanned over the surface, essentially ''tapping'' its way and gently sensing the heights of obstacles it encounters.…”

Section: How Afm Workmentioning

confidence: 99%

Macromolecular crystal growth as revealed by atomic force microscopy

McPherson

Kuznetsov

Malkin

et al. 2003

Journal of Structural Biology

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Direct visualization of macromolecular crystal growth using atomic force microscopy (AFM) has provided a powerful tool in the delineation of mechanisms and the kinetics of the growth process. It has further allowed us to evaluate the wide variety of impurities that are incorporated into crystals of proteins, nucleic acids, and viruses. We can, using AFM, image the defects and imperfections that afflict these crystals, the impurity layers that poison their surfaces, and the consequences of various factors on morphological development. All of these can be recorded under normal growth conditions, in native mother liquors, over time intervals ranging from minutes to days, and at the molecular level.

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Section: How Afm Workmentioning

confidence: 99%

Macromolecular crystal growth as revealed by atomic force microscopy

McPherson

Kuznetsov

Malkin

et al. 2003

Journal of Structural Biology

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“…The cantilever was oscillated by applying a sinusoidal voltage across the Z-direction of the scanner (22), which required minor modification of the controller electronics, performed according to the manufacturer's instructions. Best results were obtained when the cantilever was driven at a frequency range corresponding to the broad maximum of cantilever oscillation amplitude centered around 8-9 kHz (23-25).…”

Section: Atomic Force Microscopy (Afm) Of Sck/dna Complexesmentioning

confidence: 99%

Packaging of DNA by shell crosslinked nanoparticles

Thurmond

Remsen

Kowalewski³

et al. 1999

Nucleic Acids Research

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We demonstrate compaction of DNA with nanoscale biomimetic constructs which are robust synthetic analogs of globular proteins. These constructs arẽ 15 nm in diameter, shell crosslinked knedel-like (SCKs) nanoparticles, which are prepared by covalent stabilization of amphiphilic di-block co-polymer micelles, self-assembled in an aqueous solution. This synthetic approach yields size-controlled nanoparticles of persistent shape and containing positively charged functional groups at and near the particle surface. Such properties allow SCKs to bind with DNA through electrostatic interactions and facilitate reduction of the DNA hydrodynamic diameter through reversible compaction. Compaction of DNA by SCKs was evident in dynamic light scattering experiments and was directly observed by in situ atomic force microscopy. Moreover, enzymatic digestion of the DNA plasmid (pBR322, 4361 bp) by EcoRI was inhibited at low SCK:DNA ratios and prevented when ≤ ≤ ≤ ≤60 DNA bp were bound per SCK.Digestion by MspI in the presence of SCKs resulted in longer DNA fragments, indicating that not all enzyme cleavage sites were accessible within the DNA/SCK aggregates. These results have implications for the development of vehicles for successful gene therapy applications.

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“…It was then largely replaced by intermittent contact techniques like tapping mode. 5,12 These methods all involve lock-in detection and operate near a resonance frequency of the cantilever. This allows for separation of elastic and viscous responses of the surface by measuring both amplitude and phase of the cantilever motion relative to the driving signal.…”

Section: Introductionmentioning

confidence: 99%

Unexplored territory in the AFM force curve contains nanomechanics information

Eppell

Zypman

2017

AIP Advances

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We demonstrate the existence of a previously unknown damped oscillating signal just after the point when an atomic force microscope tip hits a sample surface. This oscillating signal is below the noise in a single force-displacement measurement. Autocorrelating 20 measurements using the snap to contact feature as the reference mark allows the oscillation to be clearly visible above the noise. We show that the amplitude of the signal’s oscillation is largely insensitive to the speed with which the sample is brought toward the tip proving that the impulse that generates the signal comes primarily from the snap-to-contact event. This speed-independence sets a lower limit on how softly a sample may be interrogated when measuring mechanical properties in the surface region. Collection and analysis of this damped oscillating signal eliminates the need for standard low bandwidth lock-in based techniques to determine time dependent surface mechanical properties. This allows conventional atomic force microscopes to make a single pass of force collection over a surface and, after post-processing, yield the full time dependent mechanical behavior of the surface. To demonstrate a practical use of the oscillations, we produce images of a polystyrene/polyethylene sample where the contrast mechanisms are stiffness and viscosity.

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Tapping mode atomic force microscopy in liquids

Cited by 824 publications

References 19 publications

Macromolecular crystal growth as revealed by atomic force microscopy

Macromolecular crystal growth as revealed by atomic force microscopy

Packaging of DNA by shell crosslinked nanoparticles

Unexplored territory in the AFM force curve contains nanomechanics information

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