This research contributes to broadening understanding of online retailing across electronic channels (e-channels, e.g., mobile devices) and e-channel touchpoints (e.g., mobile shopping apps) from a ...consumer perspective. Based on the multichannel retailing approach and theoretical considerations, the authors suggest an enhanced perspective on the online retailing environment and validate this multichannel e-commerce perspective by conducting both an online survey (N = 502) and an experimental study (N = 126). The results indicate that online retailing can be classified into four e-commerce categories that entail individual e-channel touchpoints, emphasizing the need for a more differentiated consideration of “the online channel.” This work advances marketing research and practice by illustrating that both technology-related quality and context-related situational benefit affect consumers' utilization of e-channels. Further findings show that retailers can enhance consumers' shopping experiences by providing alternative e-channel touchpoints (i.e., specific digital shopping formats) that contribute differently to the online customer journey.
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•A framework for the multichannel e-commerce environment•Identification of four categories of e-channels (E-, M-, IETV- and C-Commerce)•Approach to capture the online customer journey across retailer-owned touchpoints•E-channel evaluation is based on perceived quality and situational benefit.•Satisfy heterogeneous needs by designing and combining e-channel touchpoints
Structural studies of membrane proteins are still hampered by difficulties of finding appropriate membrane-mimicking media that maintain protein structure and function. Phospholipid nanodiscs seem ...promising to overcome the intrinsic problems of detergent-containing environments. While nanodiscs can offer a near-native environment, the large particle size complicates their routine use in the structural analysis of membrane proteins by solution NMR. Here, we introduce nanodiscs assembled from shorter ApoA-I protein variants that are of markedly smaller diameter and show that the resulting discs provide critical improvements for the structure determination of membrane proteins by NMR. Using the bacterial outer-membrane protein OmpX as an example, we demonstrate that the combination of small nanodisc size, high deuteration levels of protein and lipids, and the use of advanced non-uniform NMR sampling methods enable the NMR resonance assignment as well as the high-resolution structure determination of polytopic membrane proteins in a detergent-free, near-native lipid bilayer setting. By applying this method to bacteriorhodopsin, we show that our smaller nanodiscs can also be beneficial for the structural characterization of the important class of seven-transmembrane helical proteins. Our set of engineered nanodiscs of subsequently smaller diameters can be used to screen for optimal NMR spectral quality for small to medium-sized membrane proteins while still providing a functional environment. In addition to their key improvements for de novo structure determination, due to their smaller size these nanodiscs enable the investigation of interactions between membrane proteins and their (soluble) partner proteins, unbiased by the presence of detergents that might disrupt biologically relevant interactions.
A new species of darkling beetle Thraustocolus (Prothraustocola) clypealis
sp. nov.
with the new subspecies T. (P.) clypealis minor
ssp. nov.
are described from Oman and distinguished from other ...species of the genus. Images of important characters are provided for easier identification and discrimination of the new species.
Suitable membrane mimetics are crucial to the performance of structural and functional studies of membrane proteins. Phospholipid nanodiscs (formed when a membrane scaffold protein encircles a small ...portion of a lipid bilayer) have native-like membrane properties. These have been used for a variety of functional studies, but structural studies by high-resolution solution-state NMR spectroscopy of membrane proteins in commonly used nanodiscs of 10-nm diameter were limited by the high molecular weight of these particles, which caused unfavorably large NMR line widths. We have recently constructed truncated versions of the membrane scaffold protein, allowing the preparation of a range of stepwise-smaller nanodiscs (6- to 8-nm diameter) to overcome this limitation. Here, we present a protocol on the assembly of phospholipid nanodiscs of various sizes for structural studies of membrane proteins with solution-state NMR spectroscopy. We describe specific isotope-labeling schemes required for working with large membrane protein systems in nanodiscs, and provide guidelines on the setup of NMR non-uniform sampling (NUS) data acquisition and high-resolution NMR spectra reconstruction. We discuss critical points and pitfalls relating to optimization of nanodiscs for NMR spectroscopy and outline a strategy for the high-resolution structure determination and positioning of isotope-labeled membrane proteins in nanodiscs using nuclear Overhauser enhancement spectroscopy (NOESY) spectroscopy, residual dipolar couplings (RDCs) and paramagnetic relaxation enhancements (PREs). Depending on the target protein of interest, nanodisc assembly and purification can be achieved within 12-24 h. Although the focus of this protocol is on protein NMR, these nanodiscs can also be used for (cryo-) electron microscopy (EM) and small-angle X-ray and neutron-scattering studies.
In this Essay, we seek to systematically explore and understand crucial aspects of the dark side of personalized business to consumer (B2C) transactions. We identify three areas of concern. First, ...businesses increasingly engage in first-degree price discrimination, siphoning rents from consumers. Second, firms exploit widespread or idiosyncratic behavioral biases of consumers in a systematic fashion. And third, businesses use microtargeted ads and recommendations to shape consumers' preferences and steer them into a particular consumption pattern.
Siphoning rents, exploiting biases, and shaping preferences appear to be relatively distinct phenomena. However, these phenomena share a common underlying theme: the exploitation of consumers or at least an impoverishment of their lives by firms that apply novel and sophisticated technological means to maximize profits. Hence, the dark side of personalized B2C transactions may be characterized as consumers being "brought down by algorithms," losing transaction surplus, engaging in welfare-reducing transactions, and increasingly being trapped in a narrower life.
It is unclear whether first-degree price discrimination creates an efficiency problem, but surely it raises concerns of distributive justice. We propose that it should be addressed by a clear and simple warning to the consumer that she is being offered a personalized price and, in addition, a right to indicate that she does not want to participate in a personalized pricing scheme. Similarly, behavioral biases may or may not lead consumers to conclude inefficient transactions. But they should be given an opportunity to reflect on their choices if these have been induced by firms applying exploitative algorithmic sales techniques. Hence, we propose that consumers should have a right to withdraw from a contract concluded under such conditions. Finally, shaping consumers' preferences by microtargeted ads and recommendations prevents consumers from experimenting. They should have a right to opt out of the technological steering mechanisms created and utilized by firms that impoverish their lives.
Regulation along the lines proposed in this Essay is necessary because competitive markets will not protect unknowledgeable or otherwise weak consumers from exploitation. A general "right to anonymity" for consumers in the digital world could be the macrosolution to the microproblems discussed. If it were recognized and protected by the law, it might be possible to reap (most of) the benefits of personalization while avoiding (most of) its pitfalls.
Angiogenin (ANG) is a stress-activated ribonuclease that promotes the survival of motor neurons. Ribonuclease inactivating point mutations are found in a subset of patients with ALS, a fatal ...neurodegenerative disease with no cure. We recently showed that ANG cleaves tRNA within anticodon loops to produce 5′- and 3′-fragments known as tRNA-derived, stress-induced RNAs (tiRNAs). Selected 5′-tiRNAs (e.g., tiRNA ᴬˡᵃ, tiRNA Cʸˢ) cooperate with the translational repressor Y-box binding protein 1 (YB-1) to displace the cap-binding complex eIF4F from capped mRNA, inhibit translation initiation, and induce the assembly of stress granules (SGs). Here, we show that translationally active tiRNAs assemble unique G-quadruplex (G4) structures that are required for translation inhibition. We show that tiRNA ᴬˡᵃ binds the cold shock domain of YB-1 to activate these translational reprogramming events. We discovered that 5′-tiDNA ᴬˡᵃ (the DNA equivalent of 5′-tiRNA ᴬˡᵃ) is a stable tiRNA analog that displaces eIF4F from capped mRNA, inhibits translation initiation, and induces the assembly of SGs. The 5′-tiDNA ᴬˡᵃ also assembles a G4 structure that allows it to enter motor neurons spontaneously and trigger a neuroprotective response in a YB-1–dependent manner. Remarkably, the ability of 5′-tiRNA ᴬˡᵃ to induce SG assembly is inhibited by G4 structures formed by pathological GGGGCC repeats found in C9ORF72, the most common genetic cause of ALS, suggesting that functional interactions between G4 RNAs may contribute to neurodegenerative disease.
Significance Angiogenin is a stress-activated ribonuclease that cleaves tRNA to produce bioactive small noncoding RNAs tRNA-derived, stress-induced RNAs (tiRNAs) that function in a cytoprotective stress response program. Point mutations that reduce its ribonuclease activity are found in a subset of patients with ALS, a fatal neurodegenerative disease. We have found that selected tiRNAs assume G-quadruplex (G4) structures that are necessary for cytoprotective and prosurvival functions. Moreover, stable DNA analogs of these G4-containing tiRNAs spontaneously enter motor neurons and confer cytoprotection against stress. Our results identify tiRNAs as leading compounds for the development of a new class of neuroprotective drugs and give insights into the molecular mechanisms underlying the pathobiology of expanded G4-forming hexanucleotide repeats in the C9ORF72 gene.
The Fourier transform has been the gold standard for transforming data from the time domain to the frequency domain in many spectroscopic methods, including NMR spectroscopy. While reliable, it has ...the drawback that it requires a grid of uniformely sampled data points, which is not efficient for decaying signals, and it also suffers from artifacts when dealing with nondecaying signals. Over several decades, many alternative sampling and transformation schemes have been proposed. Their common problem is that relative signal amplitudes are not well-preserved. Here we demonstrate the superior performance of a sine-weighted Poisson-gap distribution sparse-sampling scheme combined with forward maximum entropy (FM) reconstruction. While the relative signal amplitudes are well-preserved, we also find that the signal-to-noise ratio is enhanced up to 4-fold per unit of data acquisition time relative to traditional linear sampling.
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•NMR yields quantitative data on the dynamics of solution-state protein structures.•NMR’s impact is enhanced by continuous innovation in assignment techniques.•Improvements in ...hardware and experimental design have extended the reach of NMR.•NMR provides access to lowly populated invisible states.•Information provided by NMR is unique and complements other biophysical techniques.
The first recognition of protein breathing was more than 50 years ago. Today, we are able to detect the multitude of interaction modes, structural polymorphisms, and binding-induced changes in protein structure that direct function. Solution-state NMR spectroscopy has proved to be a powerful technique, not only to obtain high-resolution structures of proteins, but also to provide unique insights into the functional dynamics of proteins. Here, we summarize recent technical landmarks in solution NMR that have enabled characterization of key biological macromolecular systems. These methods have been fundamental to atomic resolution structure determination and quantitative analysis of dynamics over a wide range of time scales by NMR. The ability of NMR to detect lowly populated protein conformations and transiently formed complexes plays a critical role in its ability to elucidate functionally important structural features of proteins and their dynamics.
We engineered covalently circularized nanodiscs (cNDs) which, compared with standard nanodiscs, exhibit enhanced stability, defined diameter sizes and tunable shapes. Reconstitution into cNDs ...enhanced the quality of nuclear magnetic resonance spectra for both VDAC-1, a β-barrel membrane protein, and the G-protein-coupled receptor NTR1, an α-helical membrane protein. In addition, we used cNDs to visualize how simple, nonenveloped viruses translocate their genomes across membranes to initiate infection.
The voltage-dependent anion channel (VDAC) is an essential protein in the eukaryotic outer mitochondrial membrane, providing the pore for substrate diffusion. Three high-resolution structures of the ...isoform 1 of VDAC in detergent micelles and bicelles have recently been published, using solution NMR and X-ray crystallography. They resolve longstanding discussions about the membrane topology of VDAC and provide the first eukaryotic β-barrel membrane protein structure. The structure contains a surprising feature that had not been observed in an integral membrane protein before: A parallel β-strand pairing and thus an odd number of strands. The studies also give a structural and functional basis for the voltage gating mechanism of VDAC and its modulation by NADH; however, they do not fully explain these functions yet. With the
de novo structure of VDAC-1, as well as those of half a dozen other proteins, the number of integral membrane protein structures solved by solution NMR has doubled in the past two years. Numerous further structural and functional studies on many different membrane proteins show that solution NMR has become an important tool for membrane protein molecular biology.
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