Pi‐interactions in Metalloporphyrins and Hemeproteins*

Kinetics of carbon monoxide and oxygen binding for eight electrophoretic components of sperm-whale myoglobin

“…This result may be related to the findings of Rudolph et al (1972), in which calorimetric investigations on the unfractionated myoglobin gave evidence for at least two functionally distinct components. The spectroscopic features reported by Caughey et al (1969) may also be related to our observed kinetic heterogeneity. If the charge differences on the proteins cause any changes in conformation that affect the heme site, binding is not noticeably affected except possibly for CO combination.…”

“…Previous kinetic work on whale myoglobin has been carried out only on the unfractionated protein. Infrared studies by Caughey et al (1969) suggest the possibility of heterogeneity in the binding of CO by myoglobin. Earlier studies (Gibson, 1959) suggested kinetic anomalies in the oxygen dissociation reaction.…”

Inhibition of protease-resistant prion protein formation by porphyrins and phthalocyanines

“…Both plasma proteins, such as albumin, and cytosolic proteins are known to bind some tetrapyrroles avidly (20,(35)(36)(37), which would reduce the tetrapyrrole molecules available for binding to PrP-sen and PrP-res. Furthermore, the self-association of some tetrapyrroles may also reduce the effective tetrapyrrole concentration significantly (38)(39)(40)(41)(42). Potential Mechanism of Inhibition.…”

“…These are electrostatic interactions of groups on the periphery of the core ring, protic interactions at the central nitrogens if metal-free, axial ligand binding at metal in metal complexes, and -bonding of the core aromatic ring and any peripheral aromatic rings (38,39,41,43). The large planar core aromatic ring system is likely to be an important feature because it is common to all the tetrapyrrole inhibitors, whereas the peripheral substituents and metals ions (or lack thereof) can vary widely.…”

Seven-membered rings via silyl enol ether participation in the olefin cyclization. Anti-Markownikoff cyclization in biomimetic terpene synthesis

“…After 10 min at 0 °C and 3 h at 25 °C, no starting material was left and the product from 1 turned out to be an essentially pure karahanaenone (5) (95% yield by GLC analysis).14-15 On treatment at 25 °C for 3-10 min with AICI3, Et2AlCl, T1CI4, or SnCU in hexane, the same ketone 5 was also generated in up to 85% yield (GLC analysis). 16 An overall process may be closely related to that by which the same category of cycloheptenone is believed to be formed enzymically from neryl pyrophosphate or its functional equivalent. Under the similar conditions, the bicyclic ketone 6 was produced in 65% isolated yield:8 IR (liquid film) 1705 cm-1.…”