The hummingbird's tongue: a self-assembling capillary syphon

We present the results of a combined experimental and theoretical investigation of the dynamics of drinking in ruby-throated hummingbirds. In vivo observations reveal elastocapillary deformation of the hummingbird''s tongue and capillary suction along its length. By developing a theoretical model for the hummingbird''s drinking process, we investigate how the elastocapillarity affects the energy intake rate of the bird and how its open tongue geometry reduces resistance to nectar uptake. We note that the tongue flexibility is beneficial for accessing, transporting and unloading the nectar. We demonstrate that the hummingbird can attain the fastest nectar uptake when its tongue is roughly semicircular. Finally, we assess the relative importance of capillary suction and a recently proposed fluid trapping mechanism, and conclude that the former is important in many natural settings.     

Rational design of responsive self-assembling peptides from native protein sequences

This study used identified functional native domains from spider flagelliform silk protein and the Ca(2+) binding domain of lipase Lip A from Serratia marcescens . After carefully comparing the primary structures of both sequences, we rationally designed a newly sequenced eD(2) by "hiding" the ion binding sequence in the silk structure sequence. This helped avoid redundancy, and the new sequence had properties of both model sequences. In water, eD(2) formed uniform spherical agglomerates with a β-spiral structure. Triggered by Ca(2+), eD(2) formed nanofibers with higher compliance and thermal stability. We demonstrated the specialties of this novel peptide design by changing the pH, using other metal ions, and mutating the model sequence.     

一种口腔康复治疗器设计

目的:设计一种既可用于口腔肌肉康复训练又可用于辅助治疗的口腔康复治疗器.方法:采用AUTOCAD设计出牙套,弹簧,支杆等部件,采用硅胶制作牙套,采用碳素弹簧钢丝制作菱形弹簧,采用不锈钢制作成支杆,最后组装成一个完整的口腔康复治疗器进行应用测试.结果:应用方便、感觉舒适,有效缓解了张口难度和提高张口的开启度、增加咬合力度和有效提高治疗体位稳定性.结论:该设计成果使用舒适,有效实现面肌康复和提高咬合力,减小和避免面肌纤维化和提高了治疗位置体位稳定性.     

生物芯片技术

生物芯片技术近年来发展极为迅速。生物芯片这一概念出现在２０世纪８０年代初,９０年代以来随着人类基因组计划研究的深入,生物芯片技术也得以飞速发展。本文将对生物芯片的概念、发展做一全面的叙述,并详细地介绍最新的生物芯片,如ＤＮＡ芯片等的基本原理、分类、制备,以及生物芯片的发展动向和应用前景。     

Interaction of a self-assembling peptide with oligonucleotides: complexation and aggregation

Molecular interaction of a self-assembling peptide, EAK16-II, to single- and double-stranded oligodeoxynucleotides (ODNs) was investigated under various solution conditions. The molecular events leading to EAK-ODN complexation and further aggregation were elucidated using a series of spectroscopic and microscopic methods. Despite the ability to self-assemble, EAK molecules bind to ODN molecules first upon mixing, resulting in EAK-ODN complexes. The complexes further associate to form EAK-ODN aggregates. A method based on UV-Vis absorption and centrifugation was developed to quantify the fraction of ODNs in the aggregates. The results were used to construct binding isotherms via a binding density function analysis. To compare the effects of different pH values and nucleotide types, the modified noncooperative McGhee and von Hippel model was used to extract binding parameters from the binding isotherms. The binding constant of EAK to ODNs was higher at pH 4 than at pH 7, and no binding was observed at pH 11, indicating that the interaction involved is primarily electrostatic in nature. EAK bound more strongly to single-stranded ODNs. The EAK-ODN aggregates were further visualized using atomic force microscopy; their size distribution as a function of EAK concentration was monitored by dynamic light scattering. The timescale for the EAK-ODN aggregation was on the order of minutes by fluorescence anisotropy and steady-state light scattering experiments. Fluorescence quenching experiments demonstrated that the ODNs in the aggregates were less accessible to the solvent, demonstrating a potential of oligonucleotide encapsulation by the self-assembling peptide.     

Geometrical optimisation of a biochip microchannel fluidic separator

This article reports on the geometric optimisation of a T-shaped biochip microchannel fluidic separator aiming to maximise the separation efficiency of plasma from blood through the improvement of the unbalanced separation performance among different channel bifurcations. For this purpose, an algebraic analysis is firstly implemented to identify the key parameters affecting fluid separation. A numerical optimisation is then carried out to search the key parameters for improved separation performance of the biochip. Three parameters, the interval length between bifurcations, the main channel length from the outlet to the bifurcation region and the side channel geometry, are identified as the key characteristic sizes and defined as optimisation variables. A balanced flow rate ratio between the main and side channels, which is an indication of separation effectiveness, is defined as the objective. It is found that the degradation of the separation performance is caused by the unbalanced channel resistance ratio between the main and side channel routes from bifurcations to outlets. The effects of the three key parameters can be summarised as follows: (a) shortening the interval length between bifurcations moderately reduces the differences in the flow rate ratios; (b) extending the length of the main channel from the main outlet is effective for achieving a uniformity of flow rate ratio but ineffective in changing the velocity difference of the side channels and (c) decreasing the lengths of side channels from upstream to downstream is effective for both obtaining a uniform flow rate ratio and reducing the differences in the flow velocities between the side branch channels. An optimisation process combining the three parameters is suggested as this integration approach leads to fast convergent process and also offers flexible design options for satisfying different requirements.     

The detection of a transgenic soybean biochip using gold label silver stain technology

A method for the rapid detection of transgenic soybean crops based on a combination of gene chip and "gold label silver stain" (GLSS) technologies has been established. To ensure the specificity of this method, the CaMV35S promoter and Nos terminator were selected as probes because they are both exogenous genes that are specific to transgenic soybean plants. The addition of biotin-modified dUTPs to a polymerase chain reaction (PCR) system can produce amplified nucleic acid segments containing biotin. These labeled PCR products then hybridize with specific probes on the chip and are subsequently bound by streptavidin-modified gold nanoparticles (GNPs). Due to the catalytic nature of the GNPs, silver staining can be used to visualize the hybridized probes, which appear as signals in varying shades of gray. The intensity value of the gray signals can be obtained using a general scanner. Silver staining for 10 min was determined to produce the optimal signal-to-noise ratio. In addition, this method was shown to be highly specific and had a detection sensitivity of 288.57 pg/μL.     

Geometrical optimisation of a biochip microchannel fluidic separator

This article reports on the geometric optimisation of a T-shaped biochip microchannel fluidic separator aiming to maximise the separation efficiency of plasma from blood through the improvement of the unbalanced separation performance among different channel bifurcations. For this purpose, an algebraic analysis is firstly implemented to identify the key parameters affecting fluid separation. A numerical optimisation is then carried out to search the key parameters for improved separation performance of the biochip. Three parameters, the interval length between bifurcations, the main channel length from the outlet to the bifurcation region and the side channel geometry, are identified as the key characteristic sizes and defined as optimisation variables. A balanced flow rate ratio between the main and side channels, which is an indication of separation effectiveness, is defined as the objective. It is found that the degradation of the separation performance is caused by the unbalanced channel resistance ratio between the main and side channel routes from bifurcations to outlets. The effects of the three key parameters can be summarised as follows: (a) shortening the interval length between bifurcations moderately reduces the differences in the flow rate ratios; (b) extending the length of the main channel from the main outlet is effective for achieving a uniformity of flow rate ratio but ineffective in changing the velocity difference of the side channels and (c) decreasing the lengths of side channels from upstream to downstream is effective for both obtaining a uniform flow rate ratio and reducing the differences in the flow velocities between the side branch channels. An optimisation process combining the three parameters is suggested as this integration approach leads to fast convergent process and also offers flexible design options for satisfying different requirements.     

Backbone-modified amylin derivatives: implications for amyloid inhibitor design and as template for self-assembling bionanomaterials.

This report reviews our approach to the design, synthesis and structural/morphological analysis of backbone-modified amylin(20-29) derivatives. Depending on the position in the peptide backbone and the type of amide bond isostere/modification, the amylin(20-29) peptides behave either as inhibitors of amyloid fibril formation, which are able to retard amyloid formation of native amylin(20-29), or as templates for the formation of self-assembled supramolecular structures. Molecular fine-tuning of the hydrogen-bond accepting/donating properties allows the control over the morphology of the supramolecular aggregation motifs such as helical ribbons and tapes, ribbons progressing to closed peptide nanotubes, (twisted) lamellar sheets or amyloid fibrils.     

Real time device for biosensing: design of a bacteriophage model using love acoustic waves

Love wave sensors (ST-cut quartz substrate with interdigital transducers, SiO(2) guiding layer and sensitive coating) have been receiving a great deal of attention for a few years. Indeed, the wave coupled in a guiding layer confers a high gravimetric sensitivity and the shear horizontal (SH) polarization allows to work in liquid media. In this paper, an analytical method is proposed to calculate the Love wave phase velocity and the gravimetric sensitivity for a complete multilayer structure. This allows us to optimize the Love wave devices design in order to improve their gravimetric sensitivity in liquid media. As a model for virus or bacteria detection in liquids (drinking or bathing water, food em leader ) we design a model using M13 bacteriophage. The first step is the anti-M13 (AM13) monoclonal antibody grafting, on the device surface (SiO(2)). The second step is an immunoreaction in between the M13 bacteriophage and the AM13 antibody. The Love wave device allows to detect in real time the graft of the AM13 sensitive coating, as well as the immobilization of the M13 bacteriophages. With a pH change, the M13 bacteriophages can be removed from the sensor surface, in order to be numerated as plaque forming unit (pfu). Results on the sensitivity of Love waves are compared with similar immunological works with bulk acoustic wave devices, and demonstrate the high potentialities of Love waves sensors.     

Concentration effect on the aggregation of a self-assembling oligopeptide

Concentration is a key parameter in controlling the aggregation of self-assembling oligopeptides. By investigating the concentration effects, an aggregation mechanism of EAK16-II is proposed. Depending on the critical aggregation concentration (CAC) of EAK16-II, the oligopeptide aggregates into protofibrils through seeding and/or a nucleation process. Protofibrils then associate with each other to form fibrils. The CAC was found to be approximately 0.1 mg/ml by surface tension measurements. The nanostructures of aggregates were imaged and analyzed by atomic force microscopy. Globular and fibrillar aggregates were observed, and their dimensions were further quantified. To ensure that the aggregates were formed in bulk solution, light scattering (LS) measurements were conducted to monitor the fibril formation with time. The LS profile showed two different rates of aggregation depending on whether the peptide concentration was above or below the CAC. At high concentrations, the LS intensity increased strongly at early times. At low concentrations, the LS intensity increased only slightly. Our study provides information about the nature of the oligopeptide self-assembly, which is important to the understanding of the fibrillogenesis occurring in conformational diseases and to many biomedical engineering applications.     

Improvement of design of a surgical interface using an eye tracking device

Background

Surgical interfaces are used for helping surgeons in interpretation and quantification of the patient information, and for the presentation of an integrated workflow where all available data are combined to enable optimal treatments. Human factors research provides a systematic approach to design user interfaces with safety, accuracy, satisfaction and comfort. One of the human factors research called user-centered design approach is used to develop a surgical interface for kidney tumor cryoablation. An eye tracking device is used to obtain the best configuration of the developed surgical interface.

Methods

Surgical interface for kidney tumor cryoablation has been developed considering the four phases of user-centered design approach, which are analysis, design, implementation and deployment. Possible configurations of the surgical interface, which comprise various combinations of menu-based command controls, visual display of multi-modal medical images, 2D and 3D models of the surgical environment, graphical or tabulated information, visual alerts, etc., has been developed. Experiments of a simulated cryoablation of a tumor task have been performed with surgeons to evaluate the proposed surgical interface. Fixation durations and number of fixations at informative regions of the surgical interface have been analyzed, and these data are used to modify the surgical interface.

Results

Eye movement data has shown that participants concentrated their attention on informative regions more when the number of displayed Computer Tomography (CT) images has been reduced. Additionally, the time required to complete the kidney tumor cryoablation task by the participants had been decreased with the reduced number of CT images. Furthermore, the fixation durations obtained after the revision of the surgical interface are very close to what is observed in visual search and natural scene perception studies suggesting more efficient and comfortable interaction with the surgical interface. The National Aeronautics and Space Administration Task Load Index (NASA-TLX) and Short Post-Assessment Situational Awareness (SPASA) questionnaire results have shown that overall mental workload of surgeons related with surgical interface has been low as it has been aimed, and overall situational awareness scores of surgeons have been considerably high.

Conclusions

This preliminary study highlights the improvement of a developed surgical interface using eye tracking technology to obtain the best SI configuration. The results presented here reveal that visual surgical interface design prepared according to eye movement characteristics may lead to improved usability.

     

Relation between molecular shape and the morphology of self-assembling aggregates: a simulation study

Proteins can aggregate in a wide variety of structures, both compact and extended. We present simulations of a coarse-grained anisotropic model that reproduce many of the experimentally observed aggregate structures. Conversely, all structures predicted by our model have experimental counterparts (ribbons, multistranded fibrils, and vesicles). The model we use is that of a rodlike particle with an attractive (hydrophobic) stripe on its side. Our Monte Carlo simulations show that aggregate morphologies crucially depend on two parameters. The first one is the width of the attractive stripe and the second one is a presence or absence of attractive interactions at the particle ends. These results provide us with a generic insight into the relation between the shape of protein-protein interaction potential and the morphology of protein aggregates.     

The making of a memory mechanism

Long-Term Potentiation (LTP) is akind of synaptic plasticity that manycontemporary neuroscientists believe is acomponent in mechanisms of memory. This essaydescribes the discovery of LTP and thedevelopment of the LTP research program. Thestory begins in the 1950's with the discoveryof synaptic plasticity in the hippocampus (amedial temporal lobe structure now associatedwith memory), and it ends in 1973 with thepublication of three papers sketching thefuture course of the LTP research program. Themaking of LTP was a protracted affair.Hippocampal synaptic plasticity was initiallyencountered as an experimental tool, thenreported as a curiosity, and finally includedin the ontic store of the neurosciences. Earlyresearchers were not investigating thehippocampus in search of a memory mechanism;rather, they saw the hippocampus as a usefulexperimental model or as a structure implicatedin the etiology of epilepsy. The link betweenhippocampal synaptic plasticity and learning ormemory was a separate conceptual achievement.That link was formulated in at least threedifferent ways at different times: reductively(claiming that plasticity is identical tolearning), analogically (claiming thatplasticity is an example or model of learning),and mechanistically (claiming that plasticityis a component in learning or memorymechanisms). The hypothesized link withlearning or memory, coupled with developmentsin experimental techniques and preparations,shaped how researchers understood LTP itself.By 1973, the mechanistic formulation of thelink between LTP and memory provided anabstract framework around which findings frommultiple perspectives could be integrated intoa multifield research program.