Hans Ramløv | Roskilde University (original) (raw)
Papers by Hans Ramløv
Biomacromolecules, Jan 26, 2022
The Journal of Experimental Biology, Dec 1, 1995
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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.
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.
Antifreeze Proteins Volume 2, 2020
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.
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...
Antifreeze Proteins Volume 2, 2020
Biomacromolecules, Jan 26, 2022
The Journal of Experimental Biology, Dec 1, 1995
RefDoc Refdoc est un service / is powered by. ...
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.
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.
Antifreeze Proteins Volume 2, 2020
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.
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...
Antifreeze Proteins Volume 2, 2020