Stretching single DNA-molecules with temperature-stabilized optical tweezers

This thesis consists of two parts; in the first part we performed a single-molecule force extension measurement with 10kb long DNA-molecules from phage-λ to validate the calibration and single-molecule capability of our optical tweezers instrument. Fitting the worm-like chain interpolation formula to the data revealed that ca. 71% of the DNA tethers featured a contour length within ±15% of the expected value (3.38 µm). Only 25% of the found DNA had a persistence length between 30 and 60 nm. The correct value should be within 40 to 60 nm. In the second part we designed and built a precise temperature controller to remove thermal fluctuations that cause drifting of the optical trap. The controller uses feed-forward and PID (proportional-integral-derivative) feedback to achieve 1.58 mK precision and 0.3 K absolute accuracy. During a 5 min test run it reduced drifting of the trap from 1.4 nm/min in open-loop to 0.6 nm/min in closed-loop.

Food biotechnologies in Italy: a social psychological study

This dissertation presents an analysis of the representations of food biotechnologies in Italy. The thesis uses the analysis of discourse to illustrate the articulated ways in which representations are instantiated in different contexts. The theoretical thrust of the work resides in its discussion of the basic tenets of both Social Representations Theory and Discursive Psychology. The thesis offers a detailed description of the two frameworks; affinities and difference are highlighted, and a serious effort is made to develop an integrated set of theoretical resources to answer the research questions. The thesis proposes to combine a discursive methodology with Social Representations Theory. After a description of the relevant legislative framework follows an illustration of the categories used for the textual analysis. The study proposes the textual analysis of the following data: the first declaration issued by a small Italian council rejecting biotechnologies; four texts which focus on positions taken by the Catholic Church in the matter of food biotechnologies; several transcripts from a public debate in a small community of the north west of Italy. The latter study, which included an ethnographic dimension, focuses on recordings from interviews, a focus group, a public meeting and newspaper articles. Particular attention is paid to ideological representations and to the relevance of citizenship and governance to debates about food biotechnologies.

Kotitalouden opetustilat osana kehittyvää oppimisympäristöä : asumistoiminnot ja opetussuunnitelma muutoksen määrittäjinä

Home Economics Classrooms as Part of Developing the Environment Housing Activities and Curriculums Defining Change --- The aim of the research project was to develop home economics classrooms to be flexible and versatile learning environments where household activities might be practiced according to the curriculum in different social networking situations. The research is based on the socio-cultural approach, where the functionality of the learning environment is studied specifically from an interactive learning viewpoint. The social framework is a natural starting point in home economics teaching because of the group work in classrooms. The social nature of learning thus becomes a significant part of the learning process. The study considers learning as experience based, holistic and context bound. The learning environment, i.e. home economics classrooms and the material tools there, plays a significant role in developing students skills to manage everyday life. --- The first research task was to analyze the historical development of household activities. The second research task was to develop and test criteria for functional home economics classrooms in planning both the learning environment and the students activities during lessons. The third research task was to evaluate how different professionals (commissioners, planners and teachers) use the criteria as a tool. The research consists of three parts. The first contains a historical analysis of how social changes have created tension between traditional household classrooms and new activities in homes. The historical analysis is based on housing research, regulations and instructions. For this purpose a new theoretical concept, the tension arch, was introduced. This helped in recognizing and solving problems in students activities and in developing innovations. The functionality criteria for home economics classrooms were developed based on this concept. These include technical (health, safety and technical factors), functional (ergonomic, ecological, aesthetic and economic factors) and behavioural (cooperation and interaction skills and communication technologies) criteria. --- The second part discusses how the criteria were used in renovating school buildings. Empirical data was collected from two separate schools where the activities during lessons were recorded both before and after classrooms were renovated. An analysis of both environments based on video recordings was conducted. The previously created criteria were made use of, and problematic points in functionality looked for particularly from a social interactive viewpoint. The results show that the criteria were used as a planning tool. The criteria facilitated layout and equipment solutions that support both curriculum and learning in home economics classrooms taking into consideration cooperation and interaction in the classroom. With the help of the criteria the home economics classrooms changed from closed and complicated space into integrated and open spaces where the flexibility and versatility of the learning environment was emphasized. The teacher became a facilitator and counselor instead a classroom controller. --- The third part analyses the discussions in planning meetings. These were recorded and an analysis was conducted of how the criteria and research results were used in the planning process of new home economics classrooms. The planning process was multivoiced, i.e. actors from different interest groups took part. All the previously created criteria (technical, functional and behavioural) emerged in the discussions and some of them were used as planning tools. Planning meetings turned into planning studios where boundaries between organizations were ignored and the physical learning environments were developed together with experts. The planning studios resulted in multivoiced planning which showed characteristics of collaborative and participating planning as well as producing common knowledge and shared expertise. --- KEY WORDS: physical learning environment, socio-cultural approach, tension arch, boundary crossing, collaborative planning.

Optical Tweezers for Single Molecule Biology

Molecular machinery on the micro-scale, believed to be the fundamental building blocks of life, involve forces of 1-100 pN and movements of nanometers to micrometers. Micromechanical single-molecule experiments seek to understand the physics of nucleic acids, molecular motors, and other biological systems through direct measurement of forces and displacements. Optical tweezers are a popular choice among several complementary techniques for sensitive force-spectroscopy in the field of single molecule biology. The main objective of this thesis was to design and construct an optical tweezers instrument capable of investigating the physics of molecular motors and mechanisms of protein/nucleic-acid interactions on the single-molecule level. A double-trap optical tweezers instrument incorporating acousto-optic trap-steering, two independent detection channels, and a real-time digital controller was built. A numerical simulation and a theoretical study was performed to assess the signal-to-noise ratio in a constant-force molecular motor stepping experiment. Real-time feedback control of optical tweezers was explored in three studies. Position-clamping was implemented and compared to theoretical models using both proportional and predictive control. A force-clamp was implemented and tested with a DNA-tether in presence of the enzyme lambda exonuclease. The results of the study indicate that the presented models describing signal-to-noise ratio in constant-force experiments and feedback control experiments in optical tweezers agree well with experimental data. The effective trap stiffness can be increased by an order of magnitude using the presented position-clamping method. The force-clamp can be used for constant-force experiments, and the results from a proof-of-principle experiment, in which the enzyme lambda exonuclease converts double-stranded DNA to single-stranded DNA, agree with previous research. The main objective of the thesis was thus achieved. The developed instrument and presented results on feedback control serve as a stepping stone for future contributions to the growing field of single molecule biology.