Timo Vuorela

Role of Lipids in Spheroidal High Density Lipoproteins

We study the structure and dynamics of spherical high density lipoprotein (HDL) particles through coarse-grained multi-microsecond molecular dynamics simulations. We simulate both a lipid droplet without the apolipoprotein A-I (apoA-I) and the full HDL particle including two apoA-I molecules surrounding the lipid compartment. The present models are the first ones among computational studies where the size and lipid composition of HDL are realistic, corresponding to human serum HDL. We focus on the role of lipids in HDL structure and dynamics. Particular attention is paid to the assembly of lipids and the influence of lipid-protein interactions on HDL properties. We find that the properties of lipids depend significantly on their location in the particle (core, intermediate region, surface). Unlike the hydrophobic core, the intermediate and surface regions are characterized by prominent conformational lipid order. Yet, not only the conformations but also the dynamics of lipids are found to be distinctly different in the different regions of HDL, highlighting the importance of dynamics in considering the functionalization of HDL. The structure of the lipid droplet close to the HDL-water interface is altered by the presence of apoA-Is, with most prominent changes being observed for cholesterol and polar lipids. For cholesterol, slow trafficking between the surface layer and the regimes underneath is observed. The lipid-protein interactions are strongest for cholesterol, in particular its interaction with hydrophobic residues of apoA-I. Our results reveal that not only hydrophobicity but also conformational entropy of the molecules are the driving forces in the formation of HDL structure. The results provide the first detailed structural model for HDL and its dynamics with and without apoA-I, and indicate how the interplay and competition between entropy and detailed interactions may be used in nanoparticle and drug design through self-assembly.

Design and Implementation of a Portable Long-Term Physiological Signal Recorder

This paper describes a design and implementation of a portable physiological signal recorder. The device is designed for measuring electrocardiography, bioimpedance, and users activity. The bioimpedance measures the dynamic changes in the impedance, and its main application is monitoring users respiration. Activity is measured with three-axis acceleration sensor. During the design, a special attention is paid on the devices power consumption and the target has been set to a 24-h operating time. Functionality of the implemented measurement device is proven with test measurements, which include, e.g., comparison of measurement signals against reference signals, testing the device operation under vigorous upper body movements, and during a light exercise. In order to verify the device operation during real-life activities, one full day, 24-h long, measurement is carried out. The measurement system is tested with both commercial Ag/AgCl gel-paste electrodes and custom-made textile electrodes. Device is proven to be operational with both electrodes, but textile electrodes are found to be more sensitive for movement artifacts. This paper also gives a small review of other existing portable and wearable physiological measurement devices and discusses some general requirements of these devices.

Lipid exchange mechanism of the cholesteryl ester transfer protein clarified by atomistic and coarse-grained simulations.

Cholesteryl ester transfer protein (CETP) transports cholesteryl esters, triglycerides, and phospholipids between different lipoprotein fractions in blood plasma. The inhibition of CETP has been shown to be a sound strategy to prevent and treat the development of coronary heart disease. We employed molecular dynamics simulations to unravel the mechanisms associated with the CETP-mediated lipid exchange. To this end we used both atomistic and coarse-grained models whose results were consistent with each other. We found CETP to bind to the surface of high density lipoprotein (HDL) -like lipid droplets through its charged and tryptophan residues. Upon binding, CETP rapidly (in about 10 ns) induced the formation of a small hydrophobic patch to the phospholipid surface of the droplet, opening a route from the core of the lipid droplet to the binding pocket of CETP. This was followed by a conformational change of helix X of CETP to an open state, in which we found the accessibility of cholesteryl esters to the C-terminal tunnel opening of CETP to increase. Furthermore, in the absence of helix X, cholesteryl esters rapidly diffused into CETP through the C-terminal opening. The results provide compelling evidence that helix X acts as a lid which conducts lipid exchange by alternating the open and closed states. The findings have potential for the design of novel molecular agents to inhibit the activity of CETP.

The design and implementation of electrically heated clothing

Modern fibre and textile materials and miniaturised electronic components enable implementation of smart clothes that enhance or augment the functionality of the ordinary clothing. Smart clothes together with palm top computers comprise applications that have an easy to use user interface. The paper describes the design and implementation of the electrically heated clothing prototype. The purpose of the prototype is to study the possibilities to augment the usage temperature range of the clothing by providing an additional electrical heating option. A palm top computer based user interface is also presented and compared to other alternatives. Some disadvantages and improvements are also discussed.

Bioimpedance measurement system for smart clothing

Bioimpedance of a human body produces a great dealof information about the changes of the body duringdifferent kinds of activities. According to the measuredimpedance for example the amount of water in the bodycan be derived. This kind of information would be veryuseful e.g. for many athletes. At the moment theimpedance measurement systems, intended for measuringthe human body, are quite complex, expensive, and theyare not designed for measuring a mobile user.In this research a wearable bioimpedancemeasurement system has been implemented. Themeasurement system has been integrated into a shell suit.Many tests have been carried out. From the measurementresults the behavior of the Total Body Water value can becalculated.

Capacitive indoor positioning and contact sensing for activity recognition in smart homes

In smart homes, unobtrusive monitoring of user position and activity are important but challenging tasks. With the current state of technology, this task is especially hard to carry out in private areas where video surveillance is considered undesirable or even offensive. Even though some alternative methods for passive and unobtrusive monitoring of people have been proposed in the past, we still do not have a simple method that could be used to measure user position and activities as a single practical solution. To fulfill this need, this paper presents a single privacy-preserving method to measure user position and activity which can easily be adapted to measure the subjects height and posture as well. The system proposed in this paper can locate a person at floor level and monitor the subjects interaction with common household items such as a bed, sofa, table or refrigerator. The measurement method is based on the conductivity of the human body and on capacitive coupling of low-frequency signals between electrodes embedded in the floor and the in the environment. A test system was built for the TUT Smart Home and was evaluated with multiple test subjects, including a two-week-long living test to show the systems potential in long-term monitoring applications. The results show that a standing person can be positioned to within either 7 or 11-cm accuracy at a 90% confidence level using 30 × 30-cm and 60 × 60-cm-sized transmitting floor electrodes, respectively. For people walking, the respective accuracies are 17 and 33 cm. According to the long-term test results, the interactions with the environment were detected accurately. All the test data from this long-term living test, including the persons position, contact with common household items as well as the user annotations, have been made public and are available for download.

Physiological measurements in smart clothing: a case study of total body water estimation with bioimpedance:

A wearable physiological bioimpedance measurement system has been designed and implemented. Measured bioimpedance values can be utilized for total body water (TBW) estimation. This information can be useful for, eg, athletes whose performance weakens due to dehydration. The system is integrated into a sport suit and its functionality has been tested by performing walking, fitness cycling and running tests. Also reference tests in a sauna have been performed. Altogether, nine persons have been participating in tests. During long-term exercising, TBW values were decreased. However, more tests are needed in order to analyse the measurement results accurately.

Improving human thermal comfort with smart clothing

Modem fiber techniques have enabled the implementation of truly usable smart clothes, which can aid a user to manage in specific situations by improving the functionality of the clothing.,An additional electrical heating option in the clothing widens the operating temperature range of the garment and improves the protection against cold. This paper describes the implementation of the electrical heating prototypes 1 and 2. The implementation includes also a sensor shirt for physiological signal measurements. Usability tests are made with the electrical heating prototype 1 and the results from these tests are also discussed.

User interface for social networking application for the elderly

Elderly people with no or limited skills of using computers are in risk of social isolation as social life moves to the Internet. This paper describes the design process and implementation of a user interface and device for the elderly for a social networking application. The idea is that people with no previous experience on using computers are able to use the device immediately and that the device is not considered to be a computer. An iterative and user-centred design process is used to ensure that all the needs and views from the users are taken into account. The user interface and the device have been tested in long lasting field trials and the results are presented in this paper. Based on the results the implemented device seems to qualify the needs of elder users.

Reliability of the TileTrack capacitive user tracking system in smart home environment

This paper presents a short reliability analysis of the passive and device-free human positioning system called TileTrack. The presented tracking system is fully unobtrusive and requires the user to neither to wear any tags nor to perform any special action, such as talk, to be tracked. Thus, it promotes the concept of calm technology by pushing the sensing actions to the background. The system uses capacitive measurements to determine the placement of feet on different transmitting floor segments. The systems reliability and capability to track moving humans was tested in a real apartment, and the test results are presented as well as analyzed in this paper.