• 대한화학회지
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• 제62권2호
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• pp.106-112
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• 2018

Ice-binding proteins have an affinity for ice. They create a gap between the melting and freezing points by inhibiting the growth of ice, known as thermal hysteresis (TH). Interestingly, moderately active LeIBP and hyperactive FfIBP are almost identical in primary and tertiary structures, but differ in TH activity. The TH of FfIBP is tenfold higher than that of LeIBP, due to a subtle difference in their ice-binding motifs. To further evaluate the difference in TH, the interactions were investigated by ice-etching and molecular docking. Ice-etching showed that FfIBP binds to the primary and secondary prism, pyramidal, and basal planes; previously, LeIBP was found to bind to the basal and primary prism planes. Docking analysis using shape complementarity (Sc) showed that the hyperactive FfIBP had higher Sc values for all four ice planes than LeIBP, which is comparable with TH. Docking can be used to describe the hyperactivity of IBPs.

• Fisheries and Aquatic Sciences
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• 제18권2호
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• pp.137-142
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• 2015

Antifreeze proteins and glycoproteins [AF(G)Ps] constitute a group of proteins that lower the freezing but not the melting points of aqueous solutions, enabling polar and north-temperate fish to survive in ice-laden environments. However, little is known about antifreeze activity in temperate fish; such work would extend our knowledge on the functions and evolution of AF(G)Ps. In the present study, we screened for antifreeze activity in temperate fish caught off the coast of Jumunjin ($37.89^{\circ}N$), Gangneung, Korea. Thermal hysteresis (TH) and the ability to inhibit ice recrystallization (IR) in blood, liver, and muscle samples from nine fish were examined to assess antifreeze activity. As the East Sea off the coast of Jumunjin is ice-free year round, we thought it most unlikely that the fish would express antifreeze proteins. Surprisingly, the blood of Pleurogrammus azonus and three types of tissue from Gymnocanthus herzensteini, Zoarces gilli and Kareius bicoloratus exhibited measurable TH values together with the ability to trigger characteristic morphological changes in ice crystals. Blood samples from the three species also evidenced ice recrystallization (IR) inhibition. This implies that AF(G)Ps or other antifreeze-like substances are present in temperate fish even under nonfreezing conditions. These results contribute to our understanding of the functions and origins of antifreeze activity in fish.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3791-3793
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• 2010

• Fisheries and Aquatic Sciences
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• 제19권8호
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• pp.33.1-33.7
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• 2016

Antifreeze proteins (AFPs) lower the freezing point but not the melting point of aqueous solutions by inhibiting the growth of ice crystals via an adsorption-inhibition mechanism. However, the function of type IV AFP (AFP IV) is questionable, as its antifreeze activity is on the verge of detectable limits, its physiological concentration in adult fish blood is too low to function as a biological antifreeze, and its homologues are present even in fish from tropic oceans as well as freshwater. Therefore, we speculated that AFP IV may have gained antifreeze activity not by selective pressure but by chance. To test this hypothesis, we cloned, expressed, and assayed AFP IV from cultured subtropical olive flounder (Paralichthys olivaceus), which do not require antifreeze protein for survival. Among the identified expressed sequence tags of the flounder liver sample, a 5'-deleted complementary DNA (cDNA) sequence similar to the afp4 gene of the longhorn sculpin was identified, and its full-length cDNA and genome structure were examined. The deduced amino acid sequence of flounder AFP IV shared 55, 53, 52, and 49 % identity with those of Pleuragramma antarcticum, Myoxocephalus octodecemspinosus, Myoxocephalus scorpius, and Notothenia coriiceps, respectively. Furthermore, the genomic structure of this gene was conserved with those of other known AFP IVs. Notably, the recombinant AFP IV showed a weak but distinct thermal hysteresis of $0.07{\pm}0.01^{\circ}C$ at the concentration of 0.5 mg/mL, and ice crystals in an AFP IV solution grew star-shaped, which are very similar to those obtained from other polar AFP IVs. Taken together, our results do not support the hypothesis of evolution of AFP IV by selective pressure, suggesting that the antifreeze activity of AFP IV may have been gained by chance.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2411-2414
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• 2012

• 생명과학회지
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• 제27권5호
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• pp.584-590
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• 2017

결빙방지 단백질(Antifreeze protein, AFP)은 얼음 결정에 결합하여 결정의 성장을 억제한다. AFP는 영하의 환경에서 서식하는 생물체의 생존에 필수적이다. 겨울 넙치에서 분리된 type I AFP (AFP37)는 37 개의 잔기를 가진 ${\alpha}$-나선 구조의 펩타이드이다. 본 연구에서는 활성과 수용성이 높은 짧은 AFP 조각을 개발하고자 시도하였다. 아미노-말단 15, 21 잔기의 AFP15와 21를 설계 및 합성하였다. 이들 펩타이드의 아미노-말단에 CGG를 도입한 AFP15N and 21N을 합성하고 이황화 결합을 유도함으로써 이량체 펩타이드인dAFP15N과dAFP21N을 합성하였다. 이들의 나선 함량과 결빙방지 활성을 circular dichroism (CD) 분광법과 나노리터 삼투압계로 각각 측정하였다. 합성된 펩타이드 AFP15 AFP21, AFP15N, AFP21N, dAFP15N, dAFP21N의 나선 구조 함량은 대조구인 AFP37의 49, 41, 23.8, 28, 47.9, 51.7% 수준을 보였다. 이들의 결빙방지 활성은 AFP37의 13, 7, 0.05, 5.6, 13, 11%로 나타났다. 예상과는 달리 이량체화된 펩타이드는 단량체와 비슷한 결빙방지 활성을 보였다. 이는 이량체 펩타이드가 하나의 펩타이드로 얼음과 결합하기 보다 두 개의 개별적 펩타이드로 작용함으로써 단량체와 같은 활성을 보인 것으로 생각된다. 또한 펩타이드들에 의한 별 모양의 얼음 결정 형성은 펩타이드와 얼음의 약한 결합을 시사한다.

• KSBB Journal
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• 제30권6호
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• pp.345-349
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• 2015

Antifreeze proteins (AFP) inhibit growth and recrystallization of ice, and permit organisms to survive in cold environments. The AFP from an Antarctic bacterium, Flavobacterium frigoris PS1, FfIBP (Flavobacterium frigoris icebinding protein), was produced in E. coli using a cold shock induction system. The culture temperature was shifted from $37^{\circ}C$ to $15^{\circ}C$ and a 20 L culture scale was used. The final weights of dried cell and FfIBP were estimated to be 126 g and 8.4 g, respectively. The thermal hysteresis (TH) activity ($1.53^{\circ}C$) of the produced FfIBP was 3.6-fold higher than that of the LeIBP (Leucosporidium ice-binding protein) produced in Picha. The current study demonstrates that large-scale production of FfIBP was successful and the result could be extended to further application studies using recombinant AFPs.

• KSBB Journal
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• 제29권4호
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• pp.303-306
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• 2014

Antifreeze proteins (AFP) inhibit ice growth to permit the survival of polar organisms in the cold environments. The recombinant AFP from an Antarctic bacterium, Flavobacterium frigoris PS1, FfIBP (Flavobacterium frigoris ice-binding protein), was produced using Pichia pastoris expression system. The optimum fermentation temperature ($30^{\circ}C$) and pH (5) for FfIBP production were determined using a fed-batch culture system. The maximal cell density and purified FfIBP were 112 g/L and 70 mg/L, respectively. The thermal hysteresis (TH) activity (0.85) of FfIBP obtained using a glycerol-methanol fed-batch culture system was 2-fold higher than that of the LeIBP (Leucosporidium ice-binding protein). This work allows for large-scale production of FfIBP, which could be extended to further application studies using recombinant AFPs.

• 공업화학
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• 제21권6호
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• pp.648-652
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• 2010

고정층 상압 흐름 반응기에서 메탄의 부분산화반응를 수행하여 메탄으로부터 수소제조 위한 촉매의 활성도를 평가하였고, BET, XPS, XRD를 사용하여 촉매의 특성을 분석하였다. Pd(5)/Ti-SPK과 Pd(5)/Zr-SPK 촉매의 BET 표면적, Horvath-Kawaze의 기공부피와 기공폭, t-플롯 미세기공 면적과 부피는 각각 $284m^2/g$, $0.233cm^3/g$, 3.9 nm, $30m^2/g$ $0.015cm^3/g$과 $396m^2/g$, $0.324cm^3/g$, 3.7 nm, $119m^2/g$, $0.055cm^3/g$이었다. 촉매는 히스테리시스가 잘 발달된 IV형 임을 $N_2$-흡착등온선으로부터 확인할 수 있었다. XPS분석으로부터 SPK에 Ti와 Zr이 부분 치환된 Ti-SPK과 Zr-SPK의 Si 2p과 O 1s 피크는 SPK의 Si 2p와 O 1s 피크 보다 낮은 결합에너지 쪽으로 화학 이동함을 알 수 있었고, 촉매표면의 Pd의 산화상태는 $Pd^0$와 $Pd^{+2}$이었다. XRD의 결정 피크는 반응 전에 무정형인 촉매가 반응 후에는 결정상으로 변함을 보여주었다. Pd(5)/Ti-SPK과 Pd(5)/Zr-SPK 촉매의 메탄의 전화율과 수소의 선택도는 973 K, $CH_4/O_2$ = 2, GHSV = $8.4{\times}10^4mL/g_{cat}{\cdot}h$. 반응조건에서 각각 77, 84%와 78, 72%이었고, 반응 시작 후 3일까지도 촉매의 활성이 거의 일정하게 유지되었다. Pd(5)/Ti-SPK과 Pd(5)/Zr-SPK 촉매는 메탄의 부분산화반응에서 활성도와 열 안정성 및 물리화학적 성질이 우수하였다.