Tuning liver pyruvate kinase activity up or down with a new class of allosteric modulators.

The liver isoform of pyruvate kinase (PKL) has gained interest due to its potential capacity to regulate fatty acid synthesis involved in the progression of non-alcoholic fatty liver disease (NAFLD). Here we describe a novel series of PKL modulators that can either activate or inhibit the enzyme allosterically, from a cryptic site at the interface of two protomers in the tetrameric enzyme. Starting from urolithin D, we designed and synthesised 42 new compounds. The effect of these compounds on PKL enzymatic activity was assessed after incubation with cell lysates obtained from a liver cell line. Pronounced activation of PKL activity, up to 3.8-fold, was observed for several compounds at 10 µM, while other compounds were prominent PKL inhibitors reducing its activity to 81% at best. A structure-activity relationship identified linear-shaped sulfone-sulfonamides as activators and non-linear compounds as inhibitors. Crystal structures revealed the conformations of these modulators, which were used as a reference for designing new modulators.

Serendipitous Identification of a Covalent Activator of Liver Pyruvate Kinase.

Enzymes are effective biological catalysts that accelerate almost all metabolic reactions in living organisms. Synthetic modulators of enzymes are useful tools for the study of enzymatic reactions and can provide starting points for the design of new drugs. Here, we report on the discovery of a class of biologically active compounds that covalently modifies lysine residues in human liver pyruvate kinase (PKL), leading to allosteric activation of the enzyme (EC50 =0.29 µM). Surprisingly, the allosteric activation control point resides on the lysine residue K282 present in the catalytic site of PKL. These findings were confirmed by structural data, MS/MS experiments, and molecular modelling studies. Altogether, our study provides a molecular basis for the activation mechanism and establishes a framework for further development of human liver pyruvate kinase covalent activators.

Azulene Functionalization by Iron-Mediated Addition to a Cyclohexadiene Scaffold.

The functionalization of azulenes via reaction with cationic η5-iron carbonyl diene complexes under mild reaction conditions is demonstrated. A range of azulenes, including derivatives of naturally occurring guaiazulene, were investigated in reactions with three electrophilic iron complexes of varying electronic properties, affording the desired coupling products in 43-98% yield. The products were examined with UV-vis/fluorescence spectroscopy and showed interesting halochromic properties. Decomplexation and further derivatization of the products provide access to several different classes of 1-substituted azulenes, including a conjugated ketone and a fused tetracycle.

The tree species matters: Biodiversity and ecosystem service implications of replacing Scots pine production stands with Norway spruce.

The choice of tree species used in production forests matters for biodiversity and ecosystem services. In Sweden, damage to young production forests by large browsing herbivores is helping to drive a development where sites traditionally regenerated with Scots pine (Pinus sylvestris) are instead being regenerated with Norway spruce (Picea abies). We provide a condensed synthesis of the available evidence regarding the likely resultant implications for forest biodiversity and ecosystem services from this change in tree species. Apart from some benefits (e.g. reduced stand-level browsing damage), we identified a range of negative outcomes for biodiversity, production, esthetic and recreational values, as well as increased stand vulnerability to storm, frost, and drought damage, and potentially higher risks of pest and pathogen outbreak. Our results are directly relevant to forest owners and policy-makers seeking information regarding the uncertainties, risks, and trade-offs likely to result from changing the tree species in production forests.

Pump absorption, laser amplification, and effective length in double-clad ytterbium-doped fibers with small area ratio.

We use numerical simulations with the beam propagation method (BPM) and rate equations to investigate the pump absorption and amplification characteristics in double-clad ytterbium-doped fibers with small cladding-to-core area ratios, in the range 1-3. The presence of modes with low overlap with the doped region (or alternatively, skew rays) hampers the pump absorption in a circular geometry, but we find that the effect is small for area ratios of ∼2.5 or less. We derive ray-based expressions for the small-signal absorption which show similar results. However, even when the small-signal absorption scales nearly ideally with the inverse of the area ratio, the absorption in an operating amplifier is much lower, and the dependence on the area ratio much weaker, when a large fraction of the Yb-ions is excited in a small-area-ratio fiber. We derive equations which show this, and that in contrast to conventional area ratios of, e.g., 100, the fiber length depends more strongly on the required gain than on the required pump absorption. However, fibers substantially shorter than 1 m still allow for adequate pump absorption and gain. The effective length for nonlinear interactions is less affected by this, since the Yb-excitation is low where the signal power is high. Although we treat single-mode cores, the BPM amplifier simulations show there are a few percent of the signal power in cladding-guided modes with high overlap with the Yb-doped core. Nevertheless, according to our simulations, it is possible to achieve high efficiency and mode purity with a small-area-ratio circularly symmetric double-clad fiber.

Facial reconstruction of an 11-year-old female resident of 430 BC Athens.

Although modern standards of ideal proportions and facial esthetics are based mostly on observations of human faces as depicted in Classical Greek masterpieces of art, the real faces of ordinary ancient Greeks have, until now, remained elusive and subject to the imagination. Objective forensic techniques of facial reconstruction have never been applied before, because human skeletal material from Classical Greece has been extremely scarce, since most decent burials of that time required cremation. Here, the authors show stage by stage the facial reconstruction of an 11-year-old girl whose skull was unearthed in excellent condition from a mass grave with victims of the Plague that struck Athens of 430 bc. The original skull was replicated via three-dimensional modeling and rapid prototyping techniques. The reconstruction followed the Manchester method, laying the facial tissues from the surface of the skull outward by using depth-marker pegs as thickness guides. The shape, size, and position of the eyes, ears, nose, and mouth were determined according to features of the underlying skeletal tissues, whereas the hairstyle followed the fashion of the time. This is the first case of facial reconstruction of a layperson residing in Athens of the Golden Age of Pericles. It is ironic, however, that this unfortunate girl who lived such a short life in ancient Athens, will now, 2500 years later, have the chance to travel and be universally recognizable in a world much bigger than anybody in ancient Athens could have ever imagined.