Localized singlet diradicals have attracted much attention, not only in the field of bond-homolysis chemistry, but also in nonlinear optical materials. In this study, an extremely long lived localized singlet diradical was obtained by using a new molecular design strategy in which it is kinetically stabilized by means of a macrocycle that increases the molecular strain of the corresponding σ-bonded compound. Notably, the lifetime of this diradical (14 μs) is two orders of magnitude longer than that of a standard singlet diradical without a macrocyclic structure (≈0.2 μs) at 293 K. The species is persistent below a temperature of 100 K. In addition to the kinetic stabilization of the singlet diradical, the spontaneous oxidation of its corresponding ring-closed compound at 298 K produced oxygenated products under atmospheric conditions. Apparently, the "stretch effect" induced by the macrocyclic structure plays a crucial role in extending the lifetime of localized singlet diradicals and increasing the reactivity of their corresponding σ-bonded compounds.
The matching of a bipartite graph is a structure that can be seen in various assignment problems and has long been studied. The semi-matching is an extension of the matching for a bipartite graph G = (U ∪ V, E). It is defined as a set of edges, M ⊆ E, such that each vertex in U is an endpoint of exactly one edge in M. The load-balancing problem is the problem of finding a semi-matching such that the degrees of each vertex in V are balanced. This problem is studied in the context of the task scheduling to find a "balanced" assignment of tasks for machines, and an O(|E||U |) time algorithm is proposed. On the other hand, in some practical problems, only balanced assignments are not sufficient, e.g., the assignment of wireless stations (users) to access points (APs) in wireless networks. In wireless networks, the quality of the transmission depends on the distance between a user and its AP; shorter distances are more desirable. In this paper, We formulate the min-weight load-balancing problem of finding a balanced semi-matching that minimizes the total weight for weighted bipartite graphs. We then give an optimal condition of weighted semi-matchings and propose an O(|E||U ||V |) time algorithm.
Three new polyketides, lactomycins A (1)–C (3), were isolated from the culture broth of a marine-derived Streptomyces sp. ACT232 as cathepsin B inhibitors. Their structures were determined by a combination of NMR and MS data analyses to be the dephosphorylated derivatives of a phoslactomycin class of metabolites. Lactomycins exhibited cathepsin B inhibitory activity (IC50 0.8 to 4.5 μg/mL). Even though the biosynthetic gene clusters found in the genome of the current strain have high similarity to those of phoslactomycin, neither phoslactomycins nor leustroducsins were detected by LC-MS analyses of the crude extract.
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