Search results for "laser"
showing 10 items of 3161 documents
Squaric acid mediated chemoselective PEGylation of proteins: reactivity of single-step-activated α-amino poly(ethylene glycol)s.
2012
The covalent attachment of poly(ethylene glycol) (PEG) to therapeutically active proteins (PEGylation) has become an important method to deal with the pharmacological difficulties of these polypeptides, such as short body-residence times and immunogenicity. However, the derivatives of PEG used for PEGylation lack further functional groups that would allow the addition of targeting or labeling moieties. Squaric acid diethyl ester was used for the chemoselective single-step activation of poly(ethylene glycol)s into the respective ester amides. The resultant selective protein-reactive poly(ethylene glycol)s were investigated with respect to their selectivity towards amino acid residues in bovi…
Solution nuclear magnetic resonance spectroscopy on a nanostructured diamond chip
2017
We demonstrate nuclear magnetic resonance (NMR) spectroscopy of picoliter-volume solutions with a nanostructured diamond chip. Using optical interferometric lithography, diamond surfaces were nanostructured with dense, high-aspect-ratio nanogratings, enhancing the surface area by more than a factor of 15 over mm^2 regions of the chip. The nanograting sidewalls were doped with nitrogen-vacancy (NV) centers so that more than 10 million NV centers in a (25 micrometer)^2 laser spot are located close enough to the diamond surface (5 nm) to detect the NMR spectrum of 1 pL of fluid lying within adjacent nanograting grooves. The platform was used to perform 1H and 19F NMR spectroscopy at room tempe…
Triplet-triplet energy transfer controlled by the donor-acceptor distance in rigidly held palladium-containing cofacial bisporphyrins.
2005
Eleven new complexes, including mono-, heterobi-, and homobimetallic cofacial bisporphyrins, (Pd)H 2 DPS, (M)H 2 DPX, (M)H 2 DPB, (PdZn)DPS, (PdZn)DPX, (Pt) 2 DPX, (M) 2 DPB (M=Pd, Pt), and (Pt)P (DPS 4 - = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzothiophene tetraanion, DPX 4 - = 4,5-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]-9,9-dimethylxanthene tetraanion, DPB 4 - =1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]biphenylene tetraanion, P 2 - = 5-phenyl-2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrin dianion) have been synthesized and characterized. The photophysical properties of the donor (M)P (M=Pd or Pt, P= porphy…
Novel O-antigen of Hafnia alvei PCM 1195 lipopolysaccharide with a teichoic acid-like structure
2009
Abstract The lipopolysaccharide (LPS) of Hafnia alvei strain PCM 1195 was obtained by the hot phenol/water method. The O-specific polysaccharide was released by mild acidic hydrolysis and isolated by gel filtration. The structure of the O-specific polysaccharide was investigated by 1 H, 13 C, and 31 P NMR spectroscopy, MALDI-TOF MS, and GC–MS, accompanied by monosaccharide and methylation analysis. It was concluded that the O-specific polysaccharide is composed of a hexasaccharide repeating units interlinked with a phosphate group: {→4-α- d -Glc p -(1→3)-α- l - Fuc p NAc-(1→3)-[α- d -Glc p -(1→4)]-α- d -Glc p NAc-(1→3)-α- l - Fuc p NAc-(1→4)-α- d -Glc p -(1→P} n .
End Capping Ring-Opening Olefin Metathesis Polymerization Polymers with Vinyl Lactones
2008
The selective placement of a functional group at the chain end of a ring-opening metathesis polymer using ruthenium carbene initiators has been a significant limitation. Here we demonstrate a highly effective and facile end-capping technique for ROMP with living ruthenium carbene chain ends using single-turnover olefin metathesis substrates. Vinylene carbonate and 3H-furanone are introduced as functionalization and termination agents for the ruthenium-initiated ring-opening metathesis polymerization. This leads directly to the formation of functional polymer end groups without further chemical transformation steps. Aldehyde and carboxylic acid end groups can be introduced by this new method…
How Lasers Can Help Probe the Distribution of Nuclear Magnetism
1989
Publisher Summary High-resolution atomic spectroscopy has played an important part in the study of nuclear electric and magnetic structure. Laser spectroscopy has been crucial for the measurement of isotope shifts, which reflect the variations of nuclear charge radii and shapes. High sensitivity and frequency resolution have allowed experiments to be carried out systematically over extensive ranges of stable and radioactive isotopes with lifetime as short as a few milliseconds. While the laser experiments also yield results for nuclear multipole moments, no measurements are obtained of the distribution of nuclear magnetization. Nuclear structure properties can be probed by penetrating elect…
Femtosecond formation dynamics of the spin Seebeck effect revealed by terahertz spectroscopy
2018
Understanding the transfer of spin angular momentum is essential in modern magnetism research. A model case is the generation of magnons in magnetic insulators by heating an adjacent metal film. Here, we reveal the initial steps of this spin Seebeck effect with <27fs time resolution using terahertz spectroscopy on bilayers of ferrimagnetic yttrium-iron garnet and platinum. Upon exciting the metal with an infrared laser pulse, a spin Seebeck current $j_\textrm{s}$ arises on the same ~100fs time scale on which the metal electrons thermalize. This observation highlights that efficient spin transfer critically relies on carrier multiplication and is driven by conduction electrons scattering …
Nitric oxide modulates cerebral blood flow stimulation by acetazolamide in the rat cortex: a laser Doppler scanning study
2001
Abstract The involvement of nitric oxide (NO) in cerebral blood flow (CBF) stimulation by acetazolamide was studied in anaesthetised, mechanically ventilated Wistar rats. CBF was monitored by laser Doppler scanning. Acetazolamide induced a long-lasting significant rCBF-increase. Application of N G -Nitro- l -arginine (L-NNA), an inhibitor of all NO synthetases (NOS), prevented CBF stimulation by acetazolamide. Continuous infusion of the exogenous NO donor SIN-1 (3-morpholinosydnonimine) suppressed L-NNA induced increases of mean arterial blood pressure without effect on rCBF in comparison to baseline. Additional acetazolamide injection then again caused a significant increase of rCBF in spi…
In vivo effects of an Er:YAG Laser, an ultrasonic system and scaling and root planing on the biocompatibility of periodontally diseased root surfaces…
2003
Background and Objectives The aim of the present study was to investigate the in vivo effects of an Er:YAG laser (ERL), an ultrasonic system and scaling and root planing (SRP) on the biocompatibility of periodontally diseased root surfaces in cultures of human periodontal ligament fibroblasts (PDL). Study Design/Materials and Methods Forty single rooted teeth, considered for extraction due to severe periodontal destruction, have been randomly assigned to the following groups: (1) ERL at 160 mJ/pulse and 10 Hz, or (2) Vector® ultrasonic system (VUS), or (3) SRP using hand instruments, or (4) untreated control (C). Immediately after instrumentation, all test and control teeth were extracted a…
Nifedipine improves blood flow and oxygen supply, but not steady-state oxygenation of tumours in perfusion pressure-controlled isolated limb perfusio…
2002
Isolated limb perfusion allows the direct application of therapeutic agents to a tumour-bearing extremity. The present study investigated whether the dihydropyridine-type Ca2+-channel blocker nifedipine could improve blood flow and oxygenation status of experimental tumours during isolated limb perfusion. Perfusion was performed by cannulation of the femoral artery and vein in rats bearing DS-sarcoma on the hind foot dorsum. Perfusion rate was adjusted to maintain a perfusion pressure of 100–140 mmHg throughout the experiment. Following equilibration, nifedipine was continuously infused for 30 min (8.3 μg min−1 kg−1 BW). During constant-pressure isolated limb perfusion, nifedipine can signi…