Cell membranes are dynamic structures found in all living organisms. There have been numerous constructs that model phospholipid membranes. However, unlike natural membranes, these biomimetic systems ...cannot sustain growth owing to an inability to replenish phospholipid-synthesizing catalysts. Here we report on the design and synthesis of artificial membranes embedded with synthetic, self-reproducing catalysts capable of perpetuating phospholipid bilayer formation. Replacing the complex biochemical pathways used in nature with an autocatalyst that also drives lipid synthesis leads to the continual formation of triazole phospholipids and membrane-bound oligotriazole catalysts from simpler starting materials. In addition to continual phospholipid synthesis and vesicle growth, the synthetic membranes are capable of remodeling their physical composition in response to changes in the environment by preferentially incorporating specific precursors. These results demonstrate that complex membranes capable of indefinite self-synthesis can emerge when supplied with simpler chemical building blocks.
There has been increasing interest in utilizing bottom‐up approaches to develop synthetic cells. A popular methodology is the integration of functionalized synthetic membranes with biological ...systems, producing “hybrid” artificial cells. This Concept article covers recent advances and the current state‐of‐the‐art of such hybrid systems. Specifically, we describe minimal supramolecular constructs that faithfully mimic the structure and/or function of living cells, often by controlling the assembly of highly ordered membrane architectures with defined functionality. These studies give us a deeper understanding of the nature of living systems, bring new insights into the origin of cellular life, and provide novel synthetic chassis for advancing synthetic biology.
Hybrid artificial cells: Over the last years, considerable effort has been devoted to the integration of functionalized synthetic membranes with biological systems, producing “hybrid” artificial cells. This Concept article fundamentally covers recent advances and the current state‐of‐the‐art of such hybrid systems. Specifically, the design of minimal supramolecular constructs that can faithfully mimic or reconstruct the structure and/or function of living systems is described.
We show that trigonometric identities arising from the most well known alternative to the arc-length parametrization of the circle share some of the same elaborate nature as the more familiar ...identities involving sines, tangents, etc.
The natural forms of the Leibniz rule for the $k$th derivative of a product and of Faà di Bruno's formula for the $k$th derivative of a composition involve the differential operator ...$\partial^k/\partial x_1 \cdots \partial x_k$ rather than $d^k/dx^k$, with no assumptions about whether the variables $x_1,\dots,x_k$ are all distinct, or all identical, or partitioned into several distinguishable classes of indistinguishable variables. Coefficients appearing in forms of these identities in which some variables are indistinguishable are just multiplicities of indistinguishable terms (in particular, if all variables are distinct then all coefficients are 1). The computation of the multiplicities in this generalization of Faà di Bruno's formula is a combinatorial enumeration problem that, although completely elementary, seems to have been neglected. We apply the results to cumulants of probability distributions.
Owing to the increasing intensity and frequency of wildfires in the western United States, the removal of woody debris (downed dead wood and snags) from fire‐prone landscapes is being evaluated for ...wildfire mitigation. Consequently, the study of the ecological value of coarse woody debris to sustain dependent species has become of foremost importance. From 2004–2009, we used a before‐after control‐impact (BACI) study design to assess the effects of downed wood removal on a population of big‐eared woodrats (Neotoma macrotis) in an oak woodland (Quercus spp.) in coastal‐central California, USA. Using Pollock's robust design mark‐recapture analyses (with 12 primary capture occasions represented by trapping each spring and fall, and secondary occasions composed of 3 trap nights), we estimated survival and emigration rates. Further, applying mixed‐effects models, we evaluated the effects of 7 habitat attributes on woodrat abundance and reproduction. Following the experimental removal of downed wood from the 11 randomly selected treatment plots, woodrat survival was higher (P = 0.013), and emigration was lower (P = 0.007) among 11 control plots on which downed wood was retained. Woodrat abundance within plots was best predicted by stem density, demonstrating positive demographic associations with habitat complexity. Plot‐level reproductive success (i.e., the presence of juveniles within a plot during spring) was more likely with increasing snag density. These findings indicate that snags and downed dead wood are key components of high‐quality habitat for big‐eared woodrats. Management of woody debris to mitigate wildfire risk should consider the ecological value of this habitat attribute for big‐eared woodrats and other dependent species.
From 2004–2009, we used a before‐after‐control‐impact study design to assess the effects of an experimental removal of downed wood while also evaluating the influence of other habitat attributes on a population of big‐eared woodrats (Neotoma macrotis) in otherwise undisturbed oak (Quercus spp.) woodlands in coastal‐central California. Woodrat survival, site fidelity, abundance, and reproduction were positively associated with increasing measures of habitat complexity, demonstrating that fuels management practices for wildfire mitigation need to consider the ecological benefits of snags and downed dead wood in California oak woodlands.
Transmembrane proteins are critical for signaling, transport, and metabolism, yet their reconstitution in synthetic membranes is often challenging. Non‐enzymatic and chemoselective methods to ...generate phospholipid membranes in situ would be powerful tools for the incorporation of membrane proteins. Herein, the spontaneous reconstitution of functional integral membrane proteins during the de novo synthesis of biomimetic phospholipid bilayers is described. The approach takes advantage of bioorthogonal coupling reactions to generate proteoliposomes from micelle‐solubilized proteins. This method was successfully used to reconstitute three different transmembrane proteins into synthetic membranes. This is the first example of the use of non‐enzymatic chemical synthesis of phospholipids to prepare proteoliposomes.
Membrane Proteins Inc.: The spontaneous reconstitution of functional integral membrane proteins (gray) during the de novo synthesis of biomimetic phospholipid bilayers is described. The method takes advantage of bioorthogonal coupling reactions for the non‐enzymatic generation of proteoliposomes from micelle‐solubilized proteins. This chemoselective approach results in a fast and clean reconstitution without the need for dialysis to remove excess detergent.
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