Recent developments in sample deposition and image analysis have shown that the Atomic Force Micr... more Recent developments in sample deposition and image analysis have shown that the Atomic Force Microscope is a valuable tool for the structural investigation of transcription complexes. When deposited under conditions that allow molecular equilibration onto the substrate, transcription complexes behave as worm-like chains and the mean square end-to-end distance can readily be used to determine the protein induced DNA bend angle. Measurements of the DNA contour length by means of accurate image processing procedures have revealed a DNA compaction in transcription complexes which is compatible with wrapping of the DNA against the surface of the RNA Polymerase. The methods presented have to be considered of general practical use for imaging protein-DNA complexes.
Recent developments in sample deposition and image analysis have shown that the Atomic Force Micr... more Recent developments in sample deposition and image analysis have shown that the Atomic Force Microscope is a valuable tool for the structural investigation of transcription complexes. When deposited under conditions that allow molecular equilibration onto the substrate, transcription complexes behave as worm-like chains and the mean square end-to-end distance can readily be used to determine the protein induced DNA bend angle. Measurements of the DNA contour length by means of accurate image processing procedures have revealed a DNA compaction in transcription complexes which is compatible with wrapping of the DNA against the surface of the RNA Polymerase. The methods presented have to be considered of general practical use for imaging protein-DNA complexes.
Calix[n]arenes functionalized with guanidinium groups at the upper rim and alkyl chains at the lo... more Calix[n]arenes functionalized with guanidinium groups at the upper rim and alkyl chains at the lower rim bind to DNA, condense it, and in some cases, promote cell transfection depending on their structure and lipophilicity. Atomic force microscopy (AFM) studies indicate that upon DNA binding the hydrophobic association of the lipophilic chains of cone guanidinium calix[4]arenes drives the formation of intramolecular DNA condensates, characterized by DNA loops emerging from a dense core. Furthermore, hexyl and octyl chains confer to these calixarenes cell transfection capabilities. Conversely, larger and conformationally mobile calix[6]- and calix[8]arene methoxy derivatives form intermolecular aggregates characterized by "gorgonlike" structures composed of multiple plectomenes. These adducts, in which interstrand connections are dominated by electrostatic interactions, fail to promote cell transfection. Finally, calix[4]arenes in a 1,3-alternate conformation show an intermediate behavior because they condense DNA, but the process is driven by charge-charge interactions.
Recent developments in sample deposition and image analysis have shown that the Atomic Force Micr... more Recent developments in sample deposition and image analysis have shown that the Atomic Force Microscope is a valuable tool for the structural investigation of transcription complexes. When deposited under conditions that allow molecular equilibration onto the substrate, transcription complexes behave as worm-like chains and the mean square end-to-end distance can readily be used to determine the protein induced DNA bend angle. Measurements of the DNA contour length by means of accurate image processing procedures have revealed a DNA compaction in transcription complexes which is compatible with wrapping of the DNA against the surface of the RNA Polymerase. The methods presented have to be considered of general practical use for imaging protein-DNA complexes.
Recent developments in sample deposition and image analysis have shown that the Atomic Force Micr... more Recent developments in sample deposition and image analysis have shown that the Atomic Force Microscope is a valuable tool for the structural investigation of transcription complexes. When deposited under conditions that allow molecular equilibration onto the substrate, transcription complexes behave as worm-like chains and the mean square end-to-end distance can readily be used to determine the protein induced DNA bend angle. Measurements of the DNA contour length by means of accurate image processing procedures have revealed a DNA compaction in transcription complexes which is compatible with wrapping of the DNA against the surface of the RNA Polymerase. The methods presented have to be considered of general practical use for imaging protein-DNA complexes.
Calix[n]arenes functionalized with guanidinium groups at the upper rim and alkyl chains at the lo... more Calix[n]arenes functionalized with guanidinium groups at the upper rim and alkyl chains at the lower rim bind to DNA, condense it, and in some cases, promote cell transfection depending on their structure and lipophilicity. Atomic force microscopy (AFM) studies indicate that upon DNA binding the hydrophobic association of the lipophilic chains of cone guanidinium calix[4]arenes drives the formation of intramolecular DNA condensates, characterized by DNA loops emerging from a dense core. Furthermore, hexyl and octyl chains confer to these calixarenes cell transfection capabilities. Conversely, larger and conformationally mobile calix[6]- and calix[8]arene methoxy derivatives form intermolecular aggregates characterized by "gorgonlike" structures composed of multiple plectomenes. These adducts, in which interstrand connections are dominated by electrostatic interactions, fail to promote cell transfection. Finally, calix[4]arenes in a 1,3-alternate conformation show an intermediate behavior because they condense DNA, but the process is driven by charge-charge interactions.
Uploads
Papers