Synthetic polypeptide with antifreeze activity

MUCH information has been gathered in recent years on the so-called 'antifreeze' proteins which lower the freezing point of the serum of certain marine fishes living in sub-zero water temperatures1−4. The proteins from the Antarctic fish Trematomus borchgrevinki are glycoproteins with a repeating alanyl-alanyl-threonyl tripeptide sequence, the threonyl residue being linked to a disaccharide1,2. In contrast, the antifreeze protein from the winter flounder Pseudopleuronectus americanus in the North American Atlantic coastal region is made up of eight ammo acids with no apparent repeating sequence of the residues and no sugar moiety (ref. 4 and unpublished work of C. L. Hew, C. C. Yip & G. Fletcher). The antifreeze activity of these proteins is not compatible with the known colligative properties of solutes in solution and the mechanism of their action is not yet fully understood. But a common feature of both types of the antifreeze proteins is the preponderance of alanine which accounts for over 60% of the total amino residues. This fact, together with the absence of the carbohydrate in the protein from the winter flounder, prompted us to attempt the synthesis of polypeptide analogues having comparable proportions of alanine in them along with suitable other amino acids. As a first step, we made use of the lack of any obvious periodicity in the distribution of the alanyl residues in the flounder's protein and attempted the synthesis of a random copolypeptide containing about 65 mol % of alanine and 35 mol % of aspartic acid. The choice of aspartic acid was made on the basis of its being the next major amino acid in the flounder's protein3,4 and on the expectation that its polar character will help the water-solubility of the alanine-rich copolypeptide, as in other studies on alanine-containing random copolymers. In addition, Duman and DeVries4 have earlier indicated the involvement of carboxyl groups on the antifreeze activity by chemical modification studies. We report here the synthesis of this polypeptide and show that it possesses antifreeze activity.

Silva Fennica Vol. 11, 1977.

Julkaistu Silva Fennica Vol. 11(4) -numeron liitteenä.

Taistelu yksityiskouluista: Yksityisoppikoulujen Liitto yksityisoppikouluväen puolustajana koulujärjestelmän uudistuksessa 1970-1977

Suomessa säädettiin vuonna 1968 laki koulujärjestelmän perusteista. Sen nojalla maassa siirryttiin rinnakkaiskoulujärjestelmästä kunnalliseen yhtenäiskouluun eli peruskouluun vuosina 1972-1977. Laissa varattiin yksityisille oppikouluille mahdollisuus toimia uudessa järjestelmässä, koulun omistajayhteisön niin halutessa, kunnan peruskoulua korvaavana kouluna. Vuonna 1974 lakia muutettiin siten, että kunta sai päättää, ottiko se yksityisen koulun koulusuunnitelmaansa vai ei. Suomeen jäi nelisenkymmentä yksityistä koulua, joista pääosa sijaitsi Helsingissä. Korvaavia kouluja näistä oli 24. Tässä pro gradu -tutkielmassa tarkastellaan Yksityisoppikoulujen Liiton (YOL) toimintaa peruskouluuudistuksen täytäntöönpanovuosina 1970-1977. Liiton päätavoitteena oli yksityiskoululaitoksen säilyttäminen. Pyrkimyksenä on selvittää YOL:n aiemmin lähes käyttämättömän arkistoaineiston avulla, millainen liitto oli rakenteeltaan, millaisilla intresseillä ja resursseilla se toimi ja millaisia suhdeverkostoja se koulutaistelun yhteydessä rakensi. Samalla pyritään luomaan laajempi kuva siitä, mitkä yhteiskunnalliset tahot puolustivat yksityiskoululaitoksen säilyttämistä Suomessa ja millaisin motiivein. Tästä syystä tutkimuksen lähdeaineistona hyödynnetään mm. Vapaan koulutuksen tukisäätiön arkistoaineistoa, opettajien ammattijärjestöjen lehtiä sekä peruskoulu-uudistusta koskevaa kirjallisuutta. Laadullisen verkostotutkimuksen keinoin yksityiskoululaitosta kannattaneet piirit hahmotetaan sosiaalisena verkostona, joka rakentui yhteisten intressien pohjalle. Tästä verkostosta käytetään termiä yksityisoppikouluväki. Tutkimustuloksena on, että yksityisoppikouluväki sosiaalisena verkostona rakentui ennen kaikkea ideologisten intressien pohjalle. Kyse oli pyrkimyksistä puolustaa porvarillista suomalaista yhteiskuntamuotoa ja vastustaa vasemmiston vaikutusvallan kasvua. YOL oli 1970-luvun Suomessa yksi monista porvariston taisteluelimistä. Yhdessä vuonna 1973 perustetun Vapaan koulutuksen tukisäätiön kanssa se kävi puolustustaistelua suojellakseen epäpoliittisena instituutiona pitämäänsä koululaitosta, jonka nähtiin joutuneen ideologisen hyökkäyksen kohteeksi. Yksityisoppikouluväki oli pieni, mutta sangen vaikutusvaltainen ryhmittymä. Ydinjoukko koostui muutamasta kymmenestä suomalaisen yhteiskunnan vaikuttajasta, joita yhdisti korkea koulutus, porvarillis-isänmaallinen arvomaailma ja jossain määrin myös yhteiset kokemukset sotavuosilta. Joukkoa leimasi halu rakentaa suomalaista yhteiskuntaa oman arvomaailmansa pohjalta; niin ikään se korosti kansalaisten oikeutta vapaaseen ja omaehtoiseen kasvatukseen sekä yksilölliseen omistusoikeuteen. Tavoitteessaan yksityisoppikouluväki onnistui kohtalaisesti. Ilman sen aktiviteettia ja tehokasta verkostoitumista sekä ennen muuta vahvoja poliittisia ja taloudellisia tukijoita tämä tuskin olisi onnistunut. Oman lisänsä onnistumiseen antoi julkisuuteen vuonna 1975 noussut Pirkkalan koulukokeilu, joka osaltaan lietsoi porvarillista arvomaailmaa edustavien tahojen epäluuloja vasemmiston koulutuspolitiikkaa kohtaan ja altisti heitä tukemaan yksityiskouluja. Vaikka taistelu osin onnistuikin, suurta kannatusta se ei saavuttanut. Moni näki yksityisoppikouluväen toiminnan taantumuksellisena reaktiona ja yrityksenä säilyttää vanhoja, epätasa-arvoisuutta ylläpitäviä valtarakenteita. Esiin maalailtu pelko siitä, että kunnallinen peruskoulu veisi Suomen sosialismiin, ei saanut joukkoja liikkeelle yksityiskoulujen puolesta. Esimerkiksi opettajien myönteinen suhtautuminen kunnalliseen koululaitokseen osoittaa, etteivät he pääsääntöisesti nähneet koulu-uudistuksessa tämänkaltaista ideologista vaaraa.

Concentrations and loads of some metals and fluorine in the River Kokemäenjoki in 1975 and 1977

Tiivistelmä: Metallien ja fluorin pitoisuuksista ja määristä Kokemäenjoessa vuosina 1975—1977

Monumenttikuvista elämyskuviin : Helsinki matkaesitteiden kuvituksessa 1895 - 2005

The purpose of this study is to define how Helsinki has been presented in the pictures of tourist brochures and how their illustration has changed over time. Attention is also paid to the values and meanings that the pictures mediate, as well as their historical and societal connections. The pictures are approached as representations selectively interpreting and illustrating the reality of Helsinki, while constructing mental images of it. An iconological framework structures the study. It proceeds from the description and classification of the physical features towards an analysis of time- and culture-specific meanings. The emergence of meanings and their historical and cultural underpinnings are examined from the perspectives of humanistic geography, semiotics and constructionism. In the analysis attention is paid to the discourses, myths and ideologies that underlie the representations. Information on the physical features of the pictures and their changes is collected with a content analysis. The classified data consists of 1377 photographs. These pictures are collected from 75 tourist brochures of Helsinki that have been published between 1895 and 2005. The deeper meanings of the pictures are studied qualitatively, by paying attention to the mental images that the content elements and visual effects evoke. Research studies, contemporary literature and the texts of the tourist brochures are utilised in the interpretation of the meanings. There has been a permanent core to objects of the pictures during the entire study period. It has consisted mainly of sights that are located close to the Senate and Market Squares. In addition, marine elements have been popular. The area of Helsinki represented in the brochures has extended from the Senate Square towards Töölö Bay. Pictures of monumental buildings and statues have been complemented with snapshots and portraits. In the beginning of the 20th century, brochures were mainly produced for the travelling, educated elite. The style of the pictures was declaratory and educative. They aimed at medating an objective image of the reality that prevailed in Helsinki. In practice, the pictures were connected to a patriotic ideology and the corresponding myth of Finnishness. In the second half of the 20th century the improvement of the standard of living led to a democratisation of consumers and an increase in the tourism demand. Local culture and the everyday life of "ordinary" people became popular themes in the pictures. A new welfare ideology manifested itself in the people of the local residential areas, for instance. The increase in the cultural diversity has led to the recognition of new target groups, expecially since the 1980s. The human figures in the pictures have started to function as objects of identification and a means of constructing mental images. A pronounced emphasis on experience and individuality in the illustration of the tourist brochures mirrors the post-modern change and a new ideology based on consumption. The construction and consumption of the pictures in the tourist brochures is governed by the conventions of representation and interpretaion that are typical of the genre of tourist brochures. The pictures emphasize the perceived positive characteristics of Helsinki and thus construct a skewed view of the reality. However, consumers can knowingly use the pictures as a means of dreaming and detaching themselves from their everyday reality.

Translational and rotational motion in molecular liquids: A computer simulation study of Lennard-Jones ellipsoids

In order to understand the translational and rotational motion in dense molecular liquids, detailed molecular dynamics simulations of Lennard-Jones ellipsoids have been carried out for three different values of the aspect ratio kappa. For ellipsoids with an aspect ratio equal to 2, the product of the translational diffusion coefficient (D-T) and the average orientational correlation time of the l-th rank harmonics (tau(lR)), converges to a nearly constant value at high density. Surprisingly, this density independent value of D-T tau(lR) is within 5% of the hydrodynamic prediction with the slip boundary condition. This is despite the fact that both D-T and tau(lR) themselves change nearly by an order of magnitude in the density range considered, and the rotational correlation function itself is strongly nonexponential. For small aspect ratios (kappa less than or equal to 1.5), the rotational correlation function remains largely Gaussian even at a very large density, while for a large aspect ratio (kappa greater than or equal to 3), the transition to the nematic liquid-crystalline phase precludes the hydrodynamic regime. Thus, the rotational dynamics of ellipsoids show great sensitivity to the aspect ratio. At low density, tau(lR) goes through a minimum value, indicating the role of interactions in enhancing the rate of orientational relaxation. (C) 1997 American Institute of Physics. [S0021-9606(97)50142-5].

Dependence of diffusivity on density and solute diameter in liquid phase: A molecular dynamics study of Lennard-Jones system

Investigations into the variation of self-diffusivity with solute radius, density, and degree of disorder of the host medium is explored. The system consists of a binary mixture of a relatively smaller sized solute, whose size is varied and a larger sized solvent interacting via Lennard-Jones potential. Calculations have been performed at three different reduced densities of 0.7, 0.8, and 0.933. These simulations show that diffusivity exhibits a maximum for some intermediate size of the solute when the solute diameter is varied. The maximum is found at the same size of the solute at all densities which is at variance with the prediction of the levitation effect. In order to understand this anomaly, additional simulations were carried out in which the degree of disorder has been varied while keeping the density constant. The results show that the diffusivity maximum gradually disappears with increase in disorder. Disorder has been characterized by means of the minimal spanning tree. Simulations have also been carried out in which the degree of disorder is constant and only the density is altered. The results from these simulations show that the maximum in diffusivity now shifts to larger distances with decrease in density. This is in agreement with the changes in void and neck distribution with density of the host medium. These results are in excellent agreement with the predictions of the levitation effect. They suggest that the effect of disorder is to shift the maximum in diffusivity towards smaller solute radius while that of the decrease in density is to shift it towards larger solute radius. Thus, in real systems where the degree of disorder is lower at higher density and vice versa, the effect due to density and disorder have opposing influences. These are confirmed by the changes seen in the velocity autocorrelation function, self part of the intermediate scattering function and activation energy. (C) 2012 American Institute of Physics. http://dx.doi.org/10.1063/1.3701619]

Solid-liquid transition in polydisperse Lennard-Jones systems

We study melting of a face-centered crystalline solid consisting of polydisperse Lennard-Jones spheres with Gaussian polydispersity in size. The phase diagram reproduces the existence of a nearly temperature invariant terminal polydispersity (delta(t) similar or equal to 0.11), with no signature of reentrant melting. The absence of reentrant melting can be attributed to the influence of the attractive part of the potential upon melting. We find that at terminal polydispersity the fractional density change approaches zero, which seems to arise from vanishingly small compressibility of the disordered phase. At constant temperature and volume fraction the system undergoes a sharp transition from crystalline solid to the disordered amorphous or fluid state with increasing polydispersity. This has been quantified by second- and third-order rotational invariant bond orientational order, as well as by the average inherent structure energy. The translational order parameter also indicates a similar sharp structural change at delta similar or equal to 0.09 in case of T* = 1.0, phi = 0.58. The free energy calculation further supports the sharp nature of the transition. The third-order rotationally invariant bond order shows that with increasing polydispersity, the local cluster favors a more icosahedral arrangement and the system loses its local crystalline symmetry. Interestingly, the value of structure factor S(k) of the amorphous phase at delta similar or equal to 0.10 (just beyond the solid-liquid transition density at T* = 1) becomes 2.75, which is below the value of 2.85 required for freezing given by the empirical Hansen-Verlet rule of crystallization, well known in the theory of freezing.

Use of polydispersity index as control parameter to study melting/freezing of Lennard-Jones system: Comparison among predictions of bifurcation theory with Lindemann criterion, inherent structure analysis and Hansen-Verlet rule

Using polydispersity index as an additional order parameter we investigate freezing/melting transition of Lennard-Jones polydisperse systems (with Gaussian polydispersity in size), especially to gain insight into the origin of the terminal polydispersity. The average inherent structure (IS) energy and root mean square displacement (RMSD) of the solid before melting both exhibit quite similar polydispersity dependence including a discontinuity at solid-liquid transition point. Lindemann ratio, obtained from RMSD, is found to be dependent on temperature. At a given number density, there exists a value of polydispersity index (delta (P)) above which no crystalline solid is stable. This transition value of polydispersity(termed as transition polydispersity, delta (P) ) is found to depend strongly on temperature, a feature missed in hard sphere model systems. Additionally, for a particular temperature when number density is increased, delta (P) shifts to higher values. This temperature and number density dependent value of delta (P) saturates surprisingly to a value which is found to be nearly the same for all temperatures, known as terminal polydispersity (delta (TP)). This value (delta (TP) similar to 0.11) is in excellent agreement with the experimental value of 0.12, but differs from hard sphere transition where this limiting value is only 0.048. Terminal polydispersity (delta (TP)) thus has a quasiuniversal character. Interestingly, the bifurcation diagram obtained from non-linear integral equation theories of freezing seems to provide an explanation of the existence of unique terminal polydispersity in polydisperse systems. Global bond orientational order parameter is calculated to obtain further insights into mechanism for melting.

A Lennard-Jones Embedded-Atom Potential and Its Application to the Study of Melting

The nearest-neighbour Lennard-Jones potential from the embedded-atom method is extended to a form that includes more than nearest neighbours. The model has been applied to study melting with molecular dynamics. The calculated melting point, fractional volume change on melting, heat of fusion and linear coefficients of thermal expansion are in good agreement with experimental data. We have found that the second and third neighbours influence the melting point distinctly.