Hans Ramløv

Roskilde University, Science and Environment, Faculty Member

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Professor of Comparative Animal Physiology
Research revolves around physiological and biochemical adaptations to cold and drought in ectothermic animals. Especially antifreeze proteins are investigated as well as cryptobiosis in tardigrades. Research organisms are mainly insects (Rhagium mordax) and tardigrades.
Teaching: General physiology, Adaptational physiology, Animal physiology, Comparative zoology
Phone: +45 46 74 27 79
Address: Department Of Science and Environment, build. 28.0
Roskilde University
Universitetsvej 1
P.O. Box 260
DK-4000 Roskilde
Denmark

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Final report POCEFF

by Kirsten Engell-Sørensen and Hans Ramløv

Ice Recrystallization Inhibition Is Insufficient to Explain Cryopreservation Abilities of Antifreeze Proteins

Biomacromolecules, Jan 26, 2022

Antifreeze proteins (AFPs) and glycoproteins (AFGPs) are exemplary at modifying ice crystal growt... more Antifreeze proteins (AFPs) and glycoproteins (AFGPs) are exemplary at modifying ice crystal growth and at inhibiting ice recrystallization (IRI) in frozen solutions. These properties make them highly attractive for cold storage and cryopreservation applications of biological tissue, food, and other water-based materials. The specific requirements for optimal cryostorage remain unknown, but high IRI activity has been proposed to be crucial. Here, we show that high IRI activity alone is insufficient to explain the beneficial effects of AF(G)Ps on human red blood cell (hRBC) survival. We show that AF(G)Ps with different IRI activities cause similar cell recoveries of hRBCs and that a modified AFGP variant with decreased IRI activity shows increased cell recovery. The AFGP variant was found to have enhanced interactions with a hRBC model membrane, indicating that the capability to stabilize cell membranes is another important factor for increasing the survival of cells after cryostorage. This information should be considered when designing novel synthetic cryoprotectants.

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Differential scanning calorimetry studies on the cysts of the potato-cyst nematode <i>Globodera rostochiensis</i> during freezing and melting

The Journal of Experimental Biology, Dec 1, 1995

Measuring antifreeze acitivity

Production and biochemical composition of eggs from neritic calanoid copepods reared in large outdoor tanks (Limfjord, Denmark)

Aquaculture, Mar 1, 2007

Populations of Acartia tonsa (Dana) and Centropages hamatus (Lilljeborg) were monitored in outdoo... more Populations of Acartia tonsa (Dana) and Centropages hamatus (Lilljeborg) were monitored in outdoor enclosures imitating the natural estuarine environment in northern Denmark from August 2003 to February 2004. A. tonsa was predominant in summer while C. hamatus dominated from October and onwards. Mean egg production was normally higher in C. hamatus as compared to A. tonsa and continued until late December before a decrease was observed. Hatching success remained high even in February at temperatures below zero degree indicating that no diapause eggs were produced. Further, the egg quality evaluated from the fatty acids (AA, EPA and DHA) and amino acid contents did not change markedly during the study period. From this observation it is strongly suggested that nauplii originated from copepod eggs produced throughout the monitored sampling period constitute an adequate live feed for fish larvae probably even year round.

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Vapour Pressure of Aqueous Antifreeze Glycopeptide Solutions

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Antifreeze glycoproteins from the antarctic fish Dissostichus mawsoni studied by differential scanning calorimetry (DSC) in combination with nanolitre osmometry

PubMed, May 18, 2005

This study investigates in detail the freezing events during cooling of solutions of various size... more This study investigates in detail the freezing events during cooling of solutions of various size classes of antifreeze glycoproteins. Differential scanning calorimetry and nanolitre osmometry were used to observe ice growth at temperatures within the hysteresis gap between the melting point and non-equilibrium freezing point (hysteresis freezing point) of solutions of the various sized antifreeze glycoproteins (AFGPs). The ice growth within the hysteresis gap is presumably due to both the expression of primary or near primary prism planes and also some growth at the basal plane. The binding of the AFGPs to the ice causes a particular ice crystal morphology. With the smaller AFGPs, substantial microscopic ice growth was observed in the form of a hexagonal bipyramids within the hysteresis gap.

Controlling the Freezing Process with Antifreeze Proteins

Elsevier eBooks, 2014

Abstract Antifreeze proteins (AFPs) are a relatively recently discovered group of proteins found ... more Abstract Antifreeze proteins (AFPs) are a relatively recently discovered group of proteins found in cold tolerant, cold-blooded organisms across many taxa. The proteins have apparently evolved independently multiple times as they have a wide range of primary, secondary, and tertiary structures. However, they all share the ability to recognize, bind to, and inhibit the growth of ice crystal surfaces. In the present chapter we discuss the properties of water related to freezing, the structure and physics of ice, nucleation, and recrystallization as a background for understanding the actions of antifreeze proteins, both within cold-tolerant organisms, and in the context of applications. As an inspiration and background the chapter also deals with the problems of ice formation in cold-tolerant organisms. This leads to an overview of the types of AFPs found in various organisms, with emphasis on those found in fish, insects, and plants. Antifreeze activity is defined and the antifreeze mechanism is explained, as is the binding of the AFPs to ice crystals. Antifreeze activity can be enhanced in various ways: by interaction with organic and inorganic molecules as well as by mutations of the native AFP. These enhancements may be of great importance for applying AFPs in the food industry. A section gives an overview of our present knowledge of the use of AFPs in food preservation. The physical-chemical properties of AFPs are important when dealing with applications, and as these can be quite different from other proteins a section is devoted to a discussion of these. With many new methods, both technical and bio-molecular, the future of applying AFPs in the food industry seems bright. It is our hope that by reading the present chapter the reader will feel inspired to consider AFPs as an interesting addition to old and well-proved techniques within the technologies of food processing.

Detecting seasonal variation of antifreeze protein distribution in Rhagium mordax using immunofluorescence and high resolution microscopy

Cryobiology, Feb 1, 2017

Larvae of the blackspotted pliers support beetle, Rhagium mordax, were collected monthly, for the... more Larvae of the blackspotted pliers support beetle, Rhagium mordax, were collected monthly, for the duration of 2012 and fixed. The larvae were embedded in paraffin wax and sectioned. Using fluorophore-coupled antibodies specific to the R. mordax antifreeze protein, RmAFP1, sections were visualised with UV reflected light microscopy. An automated software analysis method was developed in order to discard autofluorescence, and quantify fluorescence from bound antibodies. The results show that R. mordax cuticle and gut exhibit a higher degree of fluorophore-bound fluorescence during summer, than in the cold months. It is hypothesised that R. mordax stores RmAFP1 in, or near, the fat body during times when freeze avoidance is not needed. 1

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An open source cryostage and software analysis method for detection of antifreeze activity

Cryobiology, Jun 1, 2016

The aim of this study is to provide the reader with a simple setup that can detect antifreeze pro... more The aim of this study is to provide the reader with a simple setup that can detect antifreeze proteins (AFP) by inhibition of ice recrystallisation in very small sample sizes. This includes an open source cryostage, a method for preparing and loading samples as well as a software analysis method. The entire setup was tested using hyperactive AFP from the cerambycid beetle, Rhagium mordax. Samples containing AFP were compared to buffer samples, and the results are visualised as crystal radius evolution over time and in absolute change over 30 min. Statistical analysis showed that samples containing AFP could reliably be told apart from controls after only two minutes of recrystallisation. The goal of providing a fast, cheap and easy method for detecting antifreeze proteins in solution was met, and further development of the system can be followed at https://github.com/pechano/cryostage.

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Summary and Future Directions

Despite the fact that much progress of understanding the antifreeze proteins, AFPs, (ice-binding ... more Despite the fact that much progress of understanding the antifreeze proteins, AFPs, (ice-binding proteins ad recrystallization inhibitor proteins) has been made during the last four decades, many questions are still unanswered and each time one question is answered, more seems to appear. When studying the cold-tolerant organisms which synthesize AFPs it soon becomes clear that there is much more to be learned about the interplay between general physiology of the organisms and the physiology and natural history of their cold tolerance. AFPs are found both in circulation in the blood and in the hemolymph of various species, but they are also found in the skin and intestinal system of different fishes as well as intracellularly in a number of animals. Some isoforms of AFPs also only differ with respect to whether they are expressed with a signal peptide or not, which could indicate that they are either exported to the extracellular compartments of retained inside the cells. Thus it is not only the organism as a whole which is protected by AFPs, but specific compartments and structures which may be especially vulnerable or which are in contact with ice for very long periods are apparently specifically fortified with specific AFPs. In insects, for example, to a large extent it remains to be investigated where the different isoforms are found. As we have seen in, for example, the freeze-tolerant alpine cockroach Celattoblatta quinquemaculata AFPs are found only in association with the digestive tract. One can speculate that this is to avoid the growth of large amounts of ice in the intestine, which would draw water out of the tissues into the digestive tract leading to rupture of this as the ice crystals grow. However, this is pure speculation and experiments performed to investigate the role of AFPs in C. quinquemaculata are needed to

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Antifreeze Proteins: Environment, Systematics and Evolution

Jorden som kæmpesnebold

Physicochemical Properties of Antifreeze Proteins

Antifreeze Proteins Volume 2, 2020

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Kuldetolerance hos insekter

Antifreeze Proteins Volume 1

The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more

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Other Protective Measures of Antifreeze Proteins

Antifreeze Proteins Volume 2, 2020

The primary function of antifreeze proteins is without doubt the inhibition of ice crystal growth... more The primary function of antifreeze proteins is without doubt the inhibition of ice crystal growth in the body fluids and the inhibition of ice recrystallization in various organisms. Modification of the structure of the frozen environment by ice algae has also been reported but also this is a mechanism related to ice. However, other properties, not related to ice but still related to cold, of antifreeze proteins have been observed. These properties include interaction with cell membranes and anti-virulence properties in both animals and plants. In this chapter we present evidence that AFPs interact with both biological and model membrane systems and that these interactions rely both on the type of antifreeze protein as well as the saturation/unsaturation of the membrane lipids in question.

Referee report. For: An ice-binding protein from an Arctic grass, Leymus mollis [version 1; peer review: 3 approved]

RESEARCH ARTICLE Anhydrobiosis and Freezing-Tolerance: Adaptations That Facilitate the Establishment of Panagrolaimus Nematodes in Polar Habitats

Anhydrobiotic animals can survive the loss of both free and bound water from their cells. While i... more Anhydrobiotic animals can survive the loss of both free and bound water from their cells. While in this state they are also resistant to freezing. This physiology adapts anhydrobiotes to harsh environments and it aids their dispersal. Panagrolaimus davidi, a bacterial feeding anhydrobiotic nematode isolated from Ross Island Antarctica, can survive intracellular ice formation when fully hydrated. A capacity to survive freezing while fully hydrated has also been observed in some other Antarctic nematodes. We experimentally determined the anhydrobiotic and freezing-tolerance phenotypes of 24 Panagrolaimus strains from tropical, temperate, continental and polar habitats and we analysed their phylogenetic relationships. We found that several other Panagrolaimus isolates can also survive freezing when fully hy-drated and that tissue extracts from these freezing-tolerant nematodes can inhibit the growth of ice crystals. We show that P. davidi belongs to a clade of anhydrobiotic and freez-i...

Mutational Studies on Antifreeze Proteins

Antifreeze Proteins Volume 2, 2020

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