Loading Determination of DMTr-substituted Resins for Large-scale Oligonucleotide Synthesis.

The loading (i.e., substitution) of solid supports for oligonucleotide synthesis is an important parameter in large-scale manufacturing of oligonucleotides. Several key process parameters are dependent on the substitution of the solid support, including the number of phosphoramidite nucleoside equivalents used in the coupling step. For dimethoxytrityl (DMTr)-loaded solid supports, the substitution of the resin is determined by quantitatively cleaving the DMTr protecting group from the resin under acidic conditions and then analyzing the DMTr cation extinction by UV/vis spectroscopy. The spectrometric measurement can be performed at 409 nm or the global extinction maximum of 510 nm. The substitution is then calculated based on the Lambert-Beer law analogously to the substitution determination of Fmoc-substituted resins. Below, the determination of the molar extinction coefficient at 510 nm in a solution of 10% dichloroacetic acid in toluene and subsequent determination of the DMTr loading of DMTr-substituted resins is reported. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Determination of the molar extinction coefficient at 510 nm in DCA Deblock solution Basic Protocol 2: Substitution determination of DMTr-substituted resins by cleavage of the DMTr cation.

Mechanical Fixation by Porphyrin Connection: Synthesis and Transport Studies of a Bicyclic Dimer.

The bowl-shaped, 3-fold interlinked porphyrin dimer 2 was obtained in respectable yields during macrocyclization attempts. Its bicyclic structure, consisting of a macrocycle made of a pair of acetylene interlinked tetraphenylporphyrins which are additionally linked by a C-C bond interlinking two pyrrole subunits, has been confirmed spectroscopically (2D-NMR, UV/vis, HR-MALDI-ToF MS). Late-stage functionalization provided the structural analogue 1 with acetyl-protected terminal thiol anchor groups enabling single molecule transport investigations in a mechanically controlled break junction experiment. The formation of single-molecule junctions was observed, displaying large variations in the observed conductance values pointing at a rich diversity in the molecular junctions.

Mechanical Stabilization of Helical Chirality in a Macrocyclic Oligothiophene.

We introduce a design principle to stabilize helically chiral structures from an achiral tetrasubstituted [2.2]paracyclophane by integrating it into a macrocycle. The [2.2]paracyclophane introduces a three-dimensional perturbation into a nearly planar macrocyclic oligothiophene. The resulting helical structure is stabilized by two bulky substituents installed on the [2.2]paracyclophane unit. The increased enantiomerization barrier enabled the separation of both enantiomers. The synthesis of the target helical macrocycle 1 involves a sequence of halogenation and cross-coupling steps and a high-dilution strategy to close the macrocycle. Substituents tuning the energy of the enantiomerization process can be introduced in the last steps of the synthesis. The chiral target compound 1 was fully characterized by NMR spectroscopy and mass spectrometry. The absolute configurations of the isolated enantiomers were assigned by comparing the data of circular dichroism spectroscopy with TD-DFT calculations. The enantiomerization dynamics was studied by dynamic HPLC and variable-temperature 2D exchange spectroscopy and supported by quantum-chemical calculations.

Large Conductance Variations in a Mechanosensitive Single-Molecule Junction.

An appealing feature of molecular electronics is the possibility of inducing changes in the orbital structure through external stimuli. This can provide functionality on the single-molecule level that can be employed for sensing or switching purposes if the associated conductance changes are sizable upon application of the stimuli. Here, we show that the room-temperature conductance of a spring-like molecule can be mechanically controlled up to an order of magnitude by compressing or elongating it. Quantum-chemistry calculations indicate that the large conductance variations are the result of destructive quantum interference effects between the frontier orbitals that can be lifted by applying either compressive or tensile strain to the molecule. When periodically modulating the electrode separation, a conductance modulation at double the driving frequency is observed, providing a direct proof for the presence of quantum interference. Furthermore, oscillations in the conductance occur when the stress built up in the molecule is high enough to allow the anchoring groups to move along the surface in a stick-slip-like fashion. The mechanical control of quantum interference effects results in the largest-gauge factor reported for single-molecule devices up to now, which may open the door for applications in, e.g., a nanoscale mechanosensitive sensing device that is functional at room temperature.

Hereditary hemochromatosis: implications for South Dakota physicians.

Hereditary Hemochromatosis (HH) still causes debate among health professionals regarding appropriateness of diagnostic and screening tools. The Hemochromatosis gene (HFE) was discovered in 1996 and is now recognized to cause the majority of HH cases. A C282Y missense mutation in the HFE gene causes up to 90 percent of HH cases. In northern European populations, prevalence of heterozygosity is estimated to be as high as 10 percent, with symptomatic iron overload developing in as many as one in 200 to 300. Many guidelines regarding population screening have been proposed. It is especially important to strike a balance between allocation of healthcare resources and patient well-being in areas such as South Dakota with a large northern European and high proportion of Medicare and Medicaid patient population. This article outlines a reasonable approach to diagnosis and management for primary care physicians in South Dakota centered on a prototypical case review.

Postoperative opiate analgesia requirements of smokers and nonsmokers.

BACKGROUND: Smoking cigarettes and other forms of nicotine administration appear to blunt the perception of pain. Abrupt discontinuation of nicotine in nicotine-dependent patients appears to increase the perception of pain. The clinical importance of nicotine's effect on pain perception is not fully understood. OBJECTIVE: To determine whether smokers who abruptly discontinue smoking as a result of being hospitalized for coronary artery bypass graft (CABG) require more postoperative opiate analgesics than nonsmokers. METHODS: A retrospective review of patients who underwent a CABG was performed. Smokers (n = 20) were compared with nonsmokers (n = 69) with regard to opiate analgesic use during the first 48 hours postoperatively. The use of nonopiate sedatives was also compared between the groups. RESULTS: When normalized for weight and body mass index, smokers required 23% and 33%, respectively, more opiate analgesics than did nonsmokers (p = 0.027 and 0.023, respectively). The percentage of patients who received benzodiazepines postoperatively was similar in the 2 groups. CONCLUSIONS: In this study, smokers deprived of nicotine required a greater amount of opiates in the first 48 hours after CABG than did nonsmokers. Healthcare providers need to be aware of the potential for increased narcotic requirements among nicotine-deprived smokers. Further study is needed to determine whether nicotine replacement lessens the requirement for postoperative analgesics in smokers.