1
|
Simpson GJ, Persson M, Grill L. Adsorbate motors for unidirectional translation and transport. Nature 2023; 621:82-86. [PMID: 37673992 DOI: 10.1038/s41586-023-06384-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 06/29/2023] [Indexed: 09/08/2023]
Abstract
Artificial molecular motors are designed to transform external energy into useful work in the form of unidirectional motion1. They have been studied mainly in solution2-4, but also on solid surfaces5,6, which provide fixed reference points, allowing for tracking of their movement. However, these molecules require sophisticated design and synthesis, because the motor function must be imprinted into the chemical structure, and show reduced functionality on surfaces compared with in solution5-8. DNA walkers9,10, on the other hand, impart high directionality as they include the surface as part of the motor function, but they require chemical surface patterning and sequential solvent modification for motor activation. Here we show how efficient motors can operate at much smaller length scales on a homogeneous metal surface without any liquid. This is realized by combining a surface with a simple molecule, which, by itself, does not contain any motor unit. The motion, which is tracked at the single-molecule level, is triggered by intramolecular proton transfer with a corresponding modulation of the potential energy surface. Each molecule moves with 100 percent unidirectionality along an atomically defined straight line. Proof of the motor performing meaningful work is shown by controlled transport of single carbon monoxide molecules. This simplistic concept could form the basis for the controlled bottom-up assembly of nanostructures at the atomic scale.
Collapse
Affiliation(s)
- Grant J Simpson
- Department of Physical Chemistry, Institute of Chemistry, University of Graz, Graz, Austria
| | - Mats Persson
- Department of Chemistry, University of Liverpool, Liverpool, UK
| | - Leonhard Grill
- Department of Physical Chemistry, Institute of Chemistry, University of Graz, Graz, Austria.
| |
Collapse
|
2
|
Ramsauer B, Simpson GJ, Cartus JJ, Jeindl A, García-López V, Tour JM, Grill L, Hofmann OT. Autonomous Single-Molecule Manipulation Based on Reinforcement Learning. J Phys Chem A 2023; 127:2041-2050. [PMID: 36749194 PMCID: PMC9986865 DOI: 10.1021/acs.jpca.2c08696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Building nanostructures one-by-one requires precise control of single molecules over many manipulation steps. The ideal scenario for machine learning algorithms is complex, repetitive, and time-consuming. Here, we show a reinforcement learning algorithm that learns how to control a single dipolar molecule in the electric field of a scanning tunneling microscope. Using about 2250 iterations to train, the algorithm learned to manipulate the molecule toward specific positions on the surface. Simultaneously, it generates physical insights into the movement as well as orientation of the molecule, based on the position where the electric field is applied relative to the molecule. This reveals that molecular movement is strongly inhibited in some directions, and the torque is not symmetric around the dipole moment.
Collapse
Affiliation(s)
- Bernhard Ramsauer
- Institute
of Solid State Physics, NAWI Graz, Graz
University of Technology, Graz 8010, Austria
| | - Grant J. Simpson
- Department
of Physical Chemistry, Institute of Chemistry, NAWI Graz, University Graz, Graz 8010, Austria
| | - Johannes J. Cartus
- Institute
of Solid State Physics, NAWI Graz, Graz
University of Technology, Graz 8010, Austria
| | - Andreas Jeindl
- Institute
of Solid State Physics, NAWI Graz, Graz
University of Technology, Graz 8010, Austria
| | - Victor García-López
- Departments
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - James M. Tour
- Departments
of Chemistry and Materials Science and NanoEngineering, and the Smalley-Curl
Institute and NanoCarbon Center, Rice University, Houston, Texas 77005, United States
| | - Leonhard Grill
- Department
of Physical Chemistry, Institute of Chemistry, NAWI Graz, University Graz, Graz 8010, Austria
| | - Oliver T. Hofmann
- Institute
of Solid State Physics, NAWI Graz, Graz
University of Technology, Graz 8010, Austria
| |
Collapse
|
3
|
Civita D, Kolmer M, Simpson GJ, Li AP, Hecht S, Grill L. Control of long-distance motion of single molecules on a surface. Science 2020; 370:957-960. [PMID: 33214276 DOI: 10.1126/science.abd0696] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/27/2020] [Indexed: 11/02/2022]
Abstract
Spatial control over molecular movement is typically limited because motion at the atomic scale follows stochastic processes. We used scanning tunneling microscopy to bring single molecules into a stable orientation of high translational mobility where they moved along precisely defined tracks. Single dibromoterfluorene molecules moved over large distances of 150 nanometers with extremely high spatial precision of 0.1 angstrom across a silver (111) surface. The electrostatic nature of the effect enabled the selective application of repulsive and attractive forces to send or receive single molecules. The high control allows us to precisely move an individual and specific molecular entity between two separate probes, opening avenues for velocity measurements and thus energy dissipation studies of single molecules in real time during diffusion and collision.
Collapse
Affiliation(s)
- Donato Civita
- Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Marek Kolmer
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Grant J Simpson
- Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - An-Ping Li
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Stefan Hecht
- Department of Chemistry and IRIS Adlershof, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany.,DWI -Leibniz Institute for Interactive Materials, Forckenbeckstr. 50, 52074 Aachen, Germany.,Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringer Weg 2, 52074 Aachen, Germany
| | - Leonhard Grill
- Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria.
| |
Collapse
|
4
|
Garrido Torres JA, Simpson GJ, Adams CJ, Früchtl HA, Schaub R. On-Demand Final State Control of a Surface-Bound Bistable Single Molecule Switch. Nano Lett 2018; 18:2950-2956. [PMID: 29613810 DOI: 10.1021/acs.nanolett.8b00336] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Modern electronic devices perform their defined action because of the complete reliability of their individual active components (transistors, switches, diodes, and so forth). For instance, to encode basic computer units (bits) an electrical switch can be used. The reliability of the switch ensures that the desired outcome (the component's final state, 0 or 1) can be selected with certainty. No practical data storage device would otherwise exist. This reliability criterion will necessarily need to hold true for future molecular electronics to have the opportunity to emerge as a viable miniaturization alternative to our current silicon-based technology. Molecular electronics target the use of single-molecules to perform the actions of individual electronic components. On-demand final state control over a bistable unimolecular component has therefore been one of the main challenges in the past decade (1-5) but has yet to be achieved. In this Letter, we demonstrate how control of the final state of a surface-supported bistable single molecule switch can be realized. On the basis of the observations and deductions presented here, we further suggest an alternative strategy to achieve final state control in unimolecular bistable switches.
Collapse
Affiliation(s)
- José A Garrido Torres
- EaStCHEM and School of Chemistry , University of St. Andrews , St. Andrews KY16 9ST , United Kingdom
| | - Grant J Simpson
- EaStCHEM and School of Chemistry , University of St. Andrews , St. Andrews KY16 9ST , United Kingdom
| | - Christopher J Adams
- School of Chemistry , University of Bristol , Bristol BS8 1TS , United Kingdom
| | - Herbert A Früchtl
- EaStCHEM and School of Chemistry , University of St. Andrews , St. Andrews KY16 9ST , United Kingdom
| | - Renald Schaub
- EaStCHEM and School of Chemistry , University of St. Andrews , St. Andrews KY16 9ST , United Kingdom
| |
Collapse
|
5
|
Affiliation(s)
- Grant J Simpson
- Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Víctor García-López
- Departments of Chemistry and Materials Science and NanoEngineering, and the Smalley-Curl Institute and NanoCarbon Center, Rice University, Houston, Texas 77005, USA
| | - Philipp Petermeier
- Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Leonhard Grill
- Department of Physical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - James M Tour
- Departments of Chemistry and Materials Science and NanoEngineering, and the Smalley-Curl Institute and NanoCarbon Center, Rice University, Houston, Texas 77005, USA
| |
Collapse
|
6
|
Seljamäe-Green RT, Simpson GJ, Grillo F, Greenwood J, Francis SM, Schaub R, Gano JE, Früchtl HA, Lacovig P, Baddeley CJ. Formation of bioinorganic complexes by the corrosive adsorption of (S)-proline on Ni/Au(111). Langmuir 2014; 31:262-271. [PMID: 25495197 DOI: 10.1021/la504236w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Nickel nanoparticles modified by the adsorption of chiral amino acids are known to be effective enantioselective heterogeneous catalysts. The leaching of nickel by amino acids has a number of potential effects including the induction of chirality in the nickel atoms left behind in the nanoparticle and the creation of catalytically active nickel complexes. The adsorption of (S)-proline onto Au(111) precovered by two-dimensional nickel nanoclusters was investigated by scanning tunneling microscopy, X-ray photoelectron spectroscopy, and high-resolution electron energy loss spectroscopy. Adsorption of (S)-proline at 300 K resulted in the corrosion of the nickel clusters, the oxidation of the leached nickel, and the on-surface formation of bioinorganic complexes, which are concluded to contain three prolinate species in an octahedral arrangement around the central Ni ion. Two distinguishable forms of nickel prolinate complexes were identified. One form self-assembles into 1-D chains, and the other form gives rise to porous 2-D islands. Octahedral complexes of the type M(AB)3 are intrinsically chiral, resulting in two pairs of enantiomers. The mirror symmetry of each pair of enantiomers is broken when, as in this study, the bidentate ligand itself possesses a chiral center. DFT calculations are used to examine the relative energies of each Ni(prolinate)3 complex as isolated gas phase species and isolated adsorbed species.
Collapse
Affiliation(s)
- Riho T Seljamäe-Green
- EaStCHEM School of Chemistry, University of St. Andrews , St. Andrews, Fife KY16 9ST, U. K
| | | | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Seljamäe-Green RT, Simpson GJ, Grillo F, Greenwood J, Francis SM, Schaub R, Lacovig P, Baddeley CJ. Assembly of a chiral amino acid on an unreactive surface: (S)-proline on Au(111). Langmuir 2014; 30:3495-3501. [PMID: 24605884 DOI: 10.1021/la500336c] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The adsorption of (S)-proline on Au(111) at 300 K was studied by low-temperature scanning tunnelling microscopy, X-ray photoelectron spectroscopy, and high resolution electron energy loss spectroscopy. (S)-proline adsorbs to produce a 2-D gas phase at 300 K, which can be condensed to form ordered molecular assemblies on cooling to 77 K. The chemical nature of the self-assembled structures is discussed in light of the information provided by photoelectron and vibrational spectroscopies.
Collapse
Affiliation(s)
- Riho T Seljamäe-Green
- EaStCHEM School of Chemistry, University of St Andrews , St Andrews, Fife, KY16 9ST, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Simpson GJ, Hogan SWL, Caffio M, Adams CJ, Früchtl H, van Mourik T, Schaub R. New class of metal bound molecular switches involving H-tautomerism. Nano Lett 2014; 14:634-639. [PMID: 24471795 DOI: 10.1021/nl4038517] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A potential end-point in the miniaturization of electronic devices lies in the field of molecular electronics, where molecules perform the function of single components. To date, hydrogen tautomerism in unimolecular switches has been restricted to the central macrocycle of porphyrin-type molecules. The present work reveals how H-tautomerism is the mechanism for switching in substituted quinone derivatives, a novel class of molecules with a different chemical structure. We hence reveal that the previous restrictions applying to tautomeric molecular switches bound to a surface are not valid in general. The activation energy of switching in a prototypical quinone derivative is determined using inelastic electron tunneling. Through computational modeling, we show that the mechanism underlying this process is tautomerization of protons belonging to two amino groups. This switching property is retained upon functionalization by the addition of side groups, meaning that the switch can be chemically modified to fit specific applications.
Collapse
Affiliation(s)
- Grant J Simpson
- EaStCHEM and School of Chemistry, University of St Andrews , St Andrews, KY16 9ST, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
9
|
Jethwa SJ, Grillo F, Früchtl HA, Simpson GJ, Treanor MJ, Schaub R, Francis SM, Richardson NV, Aitken RA. Adsorption of a dihydro-TTF derivative on Au(111) via a thiolate complex bonding to gold adatoms. Chem Commun (Camb) 2014; 50:10140-3. [DOI: 10.1039/c4cc04130e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A dihydro-TTF derivative was adsorbed on Au(111) via four thiolate ligands, it is determined that relatively little charge transfer occurs between the molecule and the substrate.
Collapse
|
10
|
Closser RG, Gualtieri EJ, Newman JA, Simpson GJ. Characterization of salt interferences in second-harmonic generation detection of protein crystals. J Appl Crystallogr 2013; 46:1903-1906. [PMID: 24282335 DOI: 10.1107/s0021889813027581] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 10/09/2013] [Indexed: 11/10/2022] Open
Abstract
Studies were undertaken to assess the merits and limitations of second-harmonic generation (SHG) for the selective detection of protein and polypeptide crystal formation, focusing on the potential for false positives from SHG-active salts present in crystallization media. The SHG activities of salts commonly used in protein crystallization were measured and quantitatively compared with reference samples. Out of 19 salts investigated, six produced significant background SHG and 15 of the 96 wells of a sparse-matrix screen produced SHG upon solvent evaporation. SHG-active salts include phosphates, hydrated sulfates, formates and tartrates, while chlorides, acetates and anhydrous sulfates resulted in no detectable SHG activity. The identified SHG-active salts produced a range of signal intensities spanning nearly three orders of magnitude. However, even the weakest SHG-active salt produced signals that were several orders of magnitude greater than those produced by typical protein crystals. In general, SHG-active salts were identifiable through characteristically strong SHG and negligible two-photon-excited ultraviolet fluorescence (TPE-UVF). Exceptions included trials containing either potassium dihydrogen phosphate or ammonium formate, which produced particularly strong SHG, but with residual weak TPE-UVF signals that could potentially complicate discrimination in crystallization experiments using these precipitants.
Collapse
Affiliation(s)
- R G Closser
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907, USA
| | | | | | | |
Collapse
|
11
|
Toth SJ, Madden JT, Taylor LS, Marsac P, Simpson GJ. Selective imaging of active pharmaceutical ingredients in powdered blends with common excipients utilizing two-photon excited ultraviolet-fluorescence and ultraviolet-second order nonlinear optical imaging of chiral crystals. Anal Chem 2012; 84:5869-75. [PMID: 22816778 PMCID: PMC3590064 DOI: 10.1021/ac300917t] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Second order nonlinear optical imaging of chiral crystals (SONICC) and two-photon excited fluorescence measurements [both autofluorescence and two-photon excited UV-fluorescence (TPE-UVF)] were assessed for the selective detection of APIs relative to common pharmaceutical excipients. Active pharmaceutical ingredients (APIs) compose only a small percentage of most tabulated formulations, yet the API distribution within the tablet can affect drug release and tablet stability. Complementary measurements using either UV-SONICC (266 nm detection) or TPE-UVF were shown to generate signals >50-fold more intense for a model API (griseofulvin) than those produced by common pharmaceutical excipients. The combined product of the measurements produced signals >10(4)-fold greater than the excipients studied. UV-SONICC or TPE-UVF produced greater selectivity than analogous measurements with visible-light detection, attributed to the presence of aromatic moieties within the API exhibiting strong one and two photon absorption at ~266 nm. Complementary SONICC and fluorescence measurements allowed for the sensitive detection of the three-dimensional distribution of tadalafil within a Cialis tablet to a depth of >140 μm.
Collapse
Affiliation(s)
- S J Toth
- Department of Chemistry, College of Pharmacy, Purdue University, West Lafayette, Indiana 47907, United States
| | | | | | | | | |
Collapse
|
12
|
Gualtieri EJ, Guo F, Kissick DJ, Jose J, Kuhn RJ, Jiang W, Simpson GJ. Detection of membrane protein two-dimensional crystals in living cells. Biophys J 2011; 100:207-14. [PMID: 21190673 DOI: 10.1016/j.bpj.2010.10.051] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 10/14/2010] [Accepted: 10/18/2010] [Indexed: 12/11/2022] Open
Abstract
It is notoriously difficult to grow membrane protein crystals and solve membrane protein structures. Improved detection and screening of membrane protein crystals are needed. We have shown here that second-order nonlinear optical imaging of chiral crystals based on second harmonic generation can provide sensitive and selective detection of two-dimensional protein crystalline arrays with sufficiently low background to enable crystal detection within the membranes of live cells. The method was validated using bacteriorhodopsin crystals generated in live Halobacterium halobium bacteria and confirmed by electron microscopy from the isolated crystals. Additional studies of alphavirus glycoproteins indicated the presence of localized crystalline domains associated with virus budding from mammalian cells. These results suggest that in vivo crystallization may provide a means for expediting membrane protein structure determination for proteins exhibiting propensities for two-dimensional crystal formation.
Collapse
Affiliation(s)
- E J Gualtieri
- Department of Chemistry, Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA
| | | | | | | | | | | | | |
Collapse
|
13
|
de Lange CF, Gillis AM, Simpson GJ. Influence of threonine intake on whole-body protein deposition and threonine utilization in growing pigs fed purified diets. J Anim Sci 2001; 79:3087-95. [PMID: 11811464 DOI: 10.2527/2001.79123087x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The relationship between available threonine (Thr) intake and whole-body protein deposition (PD) was established using the serial slaughter method in 36 individually housed growing gilts between 39 and 77 kg live BW. Pigs were prescreened for their maximum PD (PDmax), based on a N balance starting at 25 kg BW while they consumed semi-ad libitum a nonlimiting diet. Pigs were fed combinations of a casein and cornstarch-based diet that was confirmed to be first-limiting in Thr and a protein-free diet starting at approximately 30 kg BW. Casein-bound Thr was provided at 60, 70, 80, 90, 100, or 120% of estimated Thr requirements for PDmax. Energy intake was kept constant across treatments and exceeded requirements for PDmax. Pigs were fed three equal meals per day; feeding levels were adjusted weekly based on BW. Pigs were killed at either 39 kg BW (n = 2 per treatment) or 77 kg BW (n = 4 per treatment) for determining chemical body composition. Composition of 39-kg BW pigs was not different across treatments (P > 0.10); therefore, an overall mean initial body composition was used to estimate body protein content at the initial BW. Across treatments, mean daily ME intake was 25.3 (SE 0.08) MJ/d and did not differ (P > 0.10) among treatments. Average daily true ileal digestible Thr intake varied between 5.33 and 9.66 g/d, representing means for pigs on the lowest and the highest Thr intakes, respectively. Mean PD was 93, 102, 118, 124, 139, and 133 (SE 4.2) g/d for pigs on the six respective treatments. Dietary Thr intake did not influence (P > 0.10) Thr content of body protein at the final BW or the partitioning of body protein between carcass, viscera, and blood. The efficiency of Thr utilization for PD was lowest (P < 0.05) at the highest Thr intake level and highest (P < 0.05) at the lowest Thr intake level. It was similar (P > 0.10) at the four intermediate Thr intake levels, in which the relationship between true ileal digestible Thr intake and PD was linear. Based on these four treatments, calculated Thr disappearance, which is closely associated with inevitable Thr catabolism, was 23.5 (SE 0.55)% of available Thr intake. This value is consistent with an efficiency of using available Thr intake above maintenance Thr requirements (54 mg/kg BW0.75) for Thr retention with PD of 73.4 (SE 1.11)%. Based on N balances conducted at approximately 40 and 75 kg BW, the marginal efficiency of Thr utilization was not influenced by BW.
Collapse
Affiliation(s)
- C F de Lange
- Department of Animal and Poultry Science, University of Guelph, ON, Canada.
| | | | | |
Collapse
|
14
|
Wilson CF, Simpson GJ, Chiu DT, Strömberg A, Orwar O, Rodriguez N, Zare RN. Nanoengineered structures for holding and manipulating liposomes and cells. Anal Chem 2001; 73:787-91. [PMID: 11248893 DOI: 10.1021/ac001020m] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe the fabrication of nanoengineered holding pipets with concave seating surfaces and fine pressure control. These pipets were shown to exhibit exceptional stability in capturing, transporting, and releasing single cells and liposomes 1-12 microm in diameter, which opens previously inaccessible avenues of research. Three specific examples demonstrated the utility and versatility of this manipulation system. In the first, carboxyrhodamine was selectively incorporated into individual cells by electroporation, after which nearly all the medium (hundreds of microliters) surrounding the docked and tagged cells was rapidly exchanged (in seconds) and the cells were subsequently probed by laser-induced fluorescence (LIF). In the second study, a single liposome containing carboxyrhodamine was transported to a dye-free solution using a transfer pipet, docked to a holding pipet, and held firmly during physical agitation and interrogation by LIF. In the third study, pairs of liposomes were positioned between two microelectrodes, held in contact, and selectively electrofused and the resulting liposomes undocked intact.
Collapse
Affiliation(s)
- C F Wilson
- Department of Chemistry, Stanford University, California 94305-5080, USA
| | | | | | | | | | | | | |
Collapse
|
15
|
Abstract
As the potential for applications utilizing oriented thin films grows, so grows the need for accurate, reliable measurements of molecular orientation and surface coverage. Recent work in our laboratory has been directed toward this goal. In this paper the theoretical and experimental effects of surface roughness and the width of the molecular orientation distribution on spectroscopically measured orientation angles are reviewed, the combination of linear and nonlinear spectroscopic techniques for accurate determination of both the mean and width of an orientation distribution is described, and the theory and methodology necessary to obtain orientation-insensitive surface coverage measurements by second harmonic generation for adsorption isotherm and kinetics investigations are reviewed.
Collapse
Affiliation(s)
- G J Simpson
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
| | | |
Collapse
|
16
|
Simpson GJ. Wellness? For whom? Clin Lab Manage Rev 1998; 12:468, 467. [PMID: 10387154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Affiliation(s)
- G J Simpson
- Department of Pathology, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
| |
Collapse
|