Immobilization and imaging of protein molecules and protein-DNA complexes on a Langmuir-Blodgett (LB) substrate have been explored here. We have prepared a nickel-arachidate (NiA) monolayer and characterized it through pressure-area isotherm on a LB trough. Recombinant RNA polymerase from Escherichia coli, where the largest subunit was replaced with the same gene having a series of histidine amino acids at the C-terminus end of the protein, was immobilized over the Ni-arachidate monolayer through a Ni(II)-histidine interaction. A single molecule of RNA polymerase could be seen through intermittent-contact atomic force microscopy (AFM). Under the condition of the formation of the LB monolayer, the enzyme molecules were arrayed and transcriptionally active. Interestingly, they could pick up sequence specific DNA molecules from the subphase in an oriented fashion. On the other hand, preformed RNA polymerase Ni(II)-arachidate monolayers bound DNA haphazardly when no surface pressure was employed.

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Oriented thin films of La 0.67 Sr 0.33 MnO 3 and La 0.67 Ca 0.33 MnO 3 were fabricated on a SrTiO 3 (002) single crystal substrate by the chemical solution deposition (CSD) process. The CSD grown films have electronic and magnetotransport properties which are comparable to those of films prepared by the pulsed laser technique and to those of the bulk single crystal samples. The magnetoresistance of the films was found to be very similar to those of pulsed laser deposition grown films and they show no contribution of grain boundaries unlike polycrystalline films. The atomic force microscopy study of the roughness and its scaling with length shows that the surfaces of the films are self affine.

Here, we report a system we have developed where long double-stranded DNAs (dsDNAs) are immobilized on a monolayer of Zn−arachidate. We have applied the Langmuir−Blodgett technique to form the monolayer of Zn−arachidate where Zn(II) is bound to arachidic acid through charge neutralization. Because tetrahedral Zn(II) participates in DNA recognition through coordination, we have been able to layer DNA over the Zn−arachidate monolayer. The DNA layer shows a typical compression and expansion cycle in a concentration-dependent fashion. Interestingly, the DNA monolayer is available for enzymatic degradation by DNaseI. The detection of DNA and its accessibility towards biological reaction is demonstrated by imaging through fluorescence microscopy. The conformation of the DNA, immobilized on the monolayer, was studied with the help of atomic force microscopy (AFM). We observed that the dsDNAs were aligned in a stretched manner on the surface. To investigate further, we also demonstrate here that the small single-stranded DNA (ssDNA) immobilized on the air−water interface can act as a target molecule for the complementary ssDNA present in the subphase. The study of DNA hybridization done with the help of fluorescence spectroscopy clearly supports the AFM characterization.