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长沙生活文章 《长沙文章(EI)》24400字

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作文一:《长沙文章(EI)》24400字

Extraction and partial characterization of pepsin-soluble collagens from

the skin of Amiurus nebulosus

Lili Chen1, a, Li Zhao1*, b, Hua Liu1, c and Runfeng Wu1, d

1School of Life Science, Jiangxi Normal University of Science and Technology, Nanchang, China

﹡ Corresponding Author

a328181539@qq., blizhao618@hotmail., c274056767@qq., dfzdg45@qq. Keywords: Skin collagen, Isolation, Characterization, Thermal stability

Abstract. Pepsin-soluble collagen (PSC) was successfully extracted from the skin of Amiurus nebulosus. The skin of Amiurus nebulosus was immersed in 0.3 mol/L acetic acid (1: 20, m: V) for 6 h at 37℃, while pepsin was added, at a level of 5000U/g dosage of defatted skin. The maximal yield of the collagen was 97.44%, which was higher than that of acid-soluble collagen (ASC) at 62.05%. Some properties of pepsin-soluble collagens from the skin of Amiurus nebulosus were characterized.  Amino acid position and SDS-PAGE suggested that the collagen might be classified as type I collagen. Moreover, FTIR investigations showed the existence of helical arrangements in PSC of Amiurus nebulosus skin of collagen. There is a possibility to use Amiurus nebulosus skin collagen as an alternative source of collagen for industrial purposes and subsequently it may maximize the economical value of the fish.

Introduction

Collagen is the most abundant protein of animal, prising approximately 30% of total animal protein [1]. It is one kind of functional proteins with extensive application in medicament and food industry fields [2]. Skins and bones of cow and pig are generally the main sources of collagen. However, Today’s health-conscious consumers, have a negative attitude toward collagen extracted from land animals because of the recent outbreaks of bovine sponge form encephalopathy (BSE), foot and mouth disease, and chicken flu. In addition, Jewish and Muslims do not consume pork-based collagen for religious reasons. Therefore, many scientists have focused their attention in finding alternative sources of collagen. Fish offal, such as bones, scales, as well as skins is very rich in collagen [3]. Many papers dealt with the practical utilization of marine animals to produce collagen

[4-8]. Recently, collagen from several fish species has been isolated and characterized [9-12]. To make more effective use of so much waste, collagens were isolated from the skin of Amiurus nebulosus and characterized for their potential in mercial applications, as alternatives to mammalian collagen in foods, cosmetics and biomedical materials.

Materials and methods

Raw material. Amiurus nebulosus skins were collected from a local fish processing factory in Jiangxi. The skins were mechanically separated with the residue of adhering tissues removed manually. After thorough mixing approximately 500 g samples of the mince were stored at -20℃ in polyethylene bags. All the reagents used in the experiment were of analytical grade.

Extraction of pepsin-soluble collagen from Amiurus nebulosus skins. All the preparative procedures were performed at 4℃. To remove the noncollagenous proteins and pigments, the skins were immersed in 5% NaCl for 24 hours, then washed with distilled water and lyophilized.

Extraction of collagen with pepsin treatment at 37℃ for 4, 6, 8 and 10 h, with solutions of 0.1, 0.3, 0.5, 0.7 and 1.0 M acetic acid at ratio of 1:10, 1:15, 1:20 and 1:25 (w/v), The pepsin dosage were 1000, 2000, 3000, 4000, 5000 and 6000U/g (enzyme activity/ quality of skins). The supernatants were centrifuged at 4℃

10,000r/min for 30 min. Then the pepsin-soluble collagen (PSC) in the supernatant

was salted out by adding NaCl to a final concentration of 0.9 M. The solution was left overnight, and the resultant precipitate, collected by centrifugation at 10000r/min for 20 min at 4 ℃, was dissolved in 0.5 M acetic acid, repeat twice, dialyzed against 0.1 M acetic acid for 1 d (1:15, v/v, changed every 4 h), distilled water for 2 d (1:15, v/v, changed every 4 h), and then lyophilized.

Determination of hydroxyproline content. The hydroxyproline content was determined after hydrolysis of the supernatant in 6 M HCl for 24 h at 110℃, using the colorimetric method remended by ISO [13]. The yield of the extraction (%) =The hydroxyproline content of the supernatant

The hydroxyproline content of the skin×100

The orthogonal experiment. Select pepsin dosage (A), dip mention time (B), acetic acid concentration (C), and solid-liquid ratio (D) for test factor, with the extraction rate of collagen for index, the L9(34) orthogonal experiment design was shown in Table 1.

Table 1. Factors and levels of the L9 (34) orthogonal experiment

Level Pepsin dosage Time Acetic acid concentration [mol/L] Solid-liquid ratio

[U/g]A [h] B C D

1 4500 6 0.2 1:15

2 5000 8 0.3 1:20

3 5500 10 0.4 1:25

Amino acid analysis. The collagen samples were hydrolyzed under vacuum with 6 M HCl at 110℃ for 24 h in the presence of 1% phenol (v/v), and the hydrolysates were analyzed with an amino acid analyzer.

Sodium dodecyl sulphate polyacylamide-gel electrophoresis (SDS-PAGE). DS-PAGE was performed by the method of Laemmli (1970) [14], using the discontinuous Tris-HCl/glycine buffer system with 7.5% resolving gel and 5% stacking gel. Proteins were stained with 0.1% (w/v) Coomassie Brilliant Blue R-250 dissolved in water, methanol and acetic acid (9:9:2, v/v/v) for 20 min, then distained using a solution containing water, methanol and acetic acid (8:1:1, v/v/v).

UV–Vis spectra. The UV–Visual absorption spectra of collagens were recorded by a spectra photometer (Model UV-754). Dried collagen was dissolved in 0.5 M acetic acid to obtain a concentration of 0.5 mg/ml and the collagen solutions were centrifuged at 5000 r/min for 10 min at 4℃. The clarified samples were determined absorbance at different wavelength (from 200 nm to 400 nm) to get UV–Vis spectra of the sample.

Fourier transforms infrared spectra (FTIR). Fourier transform infrared (FTIR) spectroscopy FTIR spectroscopy was determined as described by Muyonga etal. (2004) [1]. FTIR spectra were obtained from discs containing 2 mg collagen in approximately 100mg potassium bromide (KBr). All spectra were obtained from 4,000 to 500 cm-1 at a data acquisition rate of 2 cm-1 by using a FTIR spectrophotometer (IFS 88; Bruker, Frankfurt, Germany).

Viscosity of collagen solution. Determination of denaturation temperature was based on the method described by Kimura et al. (1988) [15] using An Ostwald’s viseter. Dried collagen was dissolved in 0.5 M acetic acid to obtain a concentration of 0.5 mg/ml. The viseter was filled with 10 ml of the sample solution, and then immersed in a water bath held at 15℃ for 30 min, to allow the collagen solution to equilibrate to the water bath temperature. The temperature was raised stepwise up to 40℃ and maintained at each temperature for 5-10 min. Collagen solution viscosities were measured at temperature intervals of about 5℃from 15℃ up to 40℃. Fractional viscosities were puted for each temperature as follows:

Fractional viscosity= F (T) =ηsp(T)-ηsp(40℃)

ηsp(15℃)-ηsp(40℃)

Where ηsp is the specific viscosity and is calculated by (t-t0)/t0. The fractional viscosities were plotted against the temperatures and the denaturation temperature was taken to be the temperature where fractional viscosity was 0.5.

Differential scanning calorimetric (DSC). Differential scanning calorimetric (DSC) was performed on a DSC PYRIS DIAMOND (American PE Company) instrument fitted with an air cooling pressor and a liquid nitrogen cooler at ambient temperature [16]. The temperature was effectively calibrated using indium as standard. Collagen fibred was weighed (3 mg) accurately and sealed in aluminum pans (BO 6.239.2–64.502). At least triplicate samples were heated from 0 to 80℃at a scanning rate of 5℃/ min, with an empty sealed pan as a reference. The shrinkage temperature was measured at the top of the transition peak.

Results and Discussion

Standard curve of hydroxyproline. Absorbance of different concentrations of hydroxyproline was determinated in 560 nm. The hydroxyproline standard curve was drawn in Fig.1. Hydroxyproline

( e

tar

tcar

txEpepsin dosageU/g raw material Fig 2.  Effect of pepsin dosage on the extraction

of collagen

Effects of different factors on extraction of pepsin-soluble collagen.

Effect of pepsin dosage on extraction ratio of collagen. Pepsin at the dosage of 3000, 4000, 5000, 6000U/g was added into fish skin solution individually. The effect of pepsin dosage on the extraction of collagen was shown in Fig.2. The extraction ratio increased with an enhancing in the dosage of pepsin from 3000 through 4000 to 5000U/g. However the dosage of pepsin was increase to 6000U/g, there was no visible change and the result was the same to the extraction ration of 5000U/g. It was therefore found that the optimal dosage of pepsin for the extraction ratio was 5000U/g.

Effect of time on the extraction ratio of collagen.  The extraction ratio of collagen from the skins was increased rapidly from 2 hour to 8 hour (Fig. 3), and then increased slowly more than 8 hour. The extraction rate of collagen from skins was 93.75% in 8 hour. It was indicated that the reaction was gone thoroughly. 1010)

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ea6t6r

rn  noi

toc4i

t4a

cr

at

rxtE2x

E2Time (h) Acetic acids concentration (mol/L)

Fig 3.  The effect of time on the extraction of Fig 4.  The effect of acetic acids concentration

collagen on the extraction of collagen

The effect of acetic acid concentration on the extraction of collagen. It was shown that the extraction ratio of collagen from the skins increased obviously in the condition of acetic acids concentration from 0.1 mol/L to 0.5 mol/L (Fig 4), but the ratio of collagen in 0.3 mol/L was closed to

in 0.5 mol/L acetic acids, then declined from 0.5 mol/L to 1.0 mol/L acetic acids, because of collagen denatured. So 0.5 mol/L acetic acids concentration was choose.

The effect of solid-liquid ratio on the extraction of collagen. It was shown that the maximal extraction rate of collagen from the skins was 94.63%, which solid-liquid ratio was 1:20 (Fig 5). The extraction of collagen from the skins was not sufficient in low liquid-solid ratio. While the liquid-solid ratio was higher, the extraction rate of collagen was not increased, but also separation and purification were difficulty. So the best solid-liquid ratio was 1:20.

%/e

tar

noitc

art

xESolid liquid ratio

Fig 5.  The effect of solid-liquid ratio on the extraction of collagen

The best technological conditions of the extraction ration of collagen from Amiurus nebulosus skin. The orthogonal bination experimental L9 (34) was selected. Results and analysis of orthogonal experiment and Variance analysis were shown in Table 2 and Table 3. The effect degree of the factors on the extraction of collagen from the skins was as follows: D>C>A>B (solid-liquid ratio > acetic acid concentration > pepsin dosage > time). The best extraction condition was: 0.3 mol/L acetic acid concentration as extraction agents, solid-liquid ratio was 1:20, pepsin dosage was 5000U/g (enzyme activity/ quality of skins) at 37℃ extract 6 hours, the rate of the collagen extraction was 97.44%. Acetic acid concentration and solid liquid ratio were extremely significant on the extraction of collagen from Amiurus nebulosus skin.

Table 2. Results and analysis of orthogonal experiment

Test number Factor

A B C D Extraction rate[%]

1 1 1 1 1 71.63

2 1 2 2 2 89.48

3 1 3 3 3 90.09

4 2 1 2 3 95.98 5 2 2 3 1 83.86

6 2

3 1 2 86.95

7 3 1 3 2 90.10

8 3 2 1 3 78.33

9 3 3 2 1 79.90

k1 83.73 85.90 78.97 78.46

k2 88.93 83.89 88.35 88.84

k3 82.78 85.65 88.02 88.13

R 6.15 2.01 9.38 10.38

Table 3. Variance analysis of orthogonal experiment

Variance source Sum-of-squares Degree of freedom Mean

square F significant

Pepsin dosage 194.577 2 97.288 5.916 *

time 22.162 2 11.081 0.674

Acetic acid

concentration 519.895 2 259.95 15.81 ** Solid-liquid ratio 597.000 2 298.50 18.15 **

Error 296.021 18 16.446

Corrected total 1629.66 26

Amino acid position. The amino acid position of Amiurus nebulosus skin pepsin-soluble collagen was shown in Table 4. Pepsin-soluble collagen was rich in glycine, proline and glutamic acid, but poor in leucine and phenylalanine. Glycine was the most abundant amino acid in Amiurus nebulosus skin collagen although it was only 22.78%, significantly lower than that of Gariepinus spp

[17] and channel cafish [18] , but similar to that of Nile perch [19-20]. Cysteine was found little in the collagen, and methionine, tyrosine and histidine were low just like many fish species collagens

[21-24]. A significant observation was the higher total imino acid content of 21.05%, which was more than  that in cold-water fish species of 16-18% [23, 25-26], but lower than that in tilapia of 25.4% [22] which was the highest in fish collagens. The essential amino acid (Threonine, Valine, Methionine, Isoleucine, Leucine, Phenylalanine, Lysine, and tryptophan) content was 17.88%. The semi-essential amino acid (Histidine, Arginine) content was 9.06%.

The higher imino acid content and higher denaturation temperature of collagen of Amiurus nebulosus, in parison with cold-water fish species are in agreement with observations by Rigby (1968) [27] that thermal stability of collagen increases with imino acid content.

Table 4. Amino acid position of

pepsin-soluble collagens from the skin of

Amiurus nebulosus

Amino acid Pepsin-soluble collagen[%]

Aspartic acid 5.62

Glutamic acid 10.03

Serine 3.91

Histidine 0.98

Arginine 8.08

Glycine 22.78

Threonine 3.47

Proline 12.33

Alanine 9.01

Valine 2.64

Methionine 1.02

Cystine 0.05

Isoleucine 1.78

Leucine 2.89  Phenylalanine 2.22                            1                   2            3

Lysine 3.66 Fig 6.  SDS-PAGE patterns of ASC and PSC Tyrosine 0.64 from the skin of Amiurus nebulosus line 1: high tryptophan 0.20 molecular weight marker; line 2: Amiurus Hydroxyproline 8.72 nebulosus skin ASC; line 3 Amiurus nebulosus

Total 100 skin PSC

SDS-polyacrylamide gel electrophoresis (SDS-PAGE). SDS-PAGE showed that pepsin-soluble collagen from the skin of Amiurus nebulosus consisted of α chains and their dimmers (β chains) (Fig

6). The α ponents showed two distinct species varying in their mobility. This was similar to the pattern observed in several other fish species [27-29].and was typical of type I collagen [30].It indicated that the pepsin-soluble collagen from Amiurus nebulosus skin appearing to type I collagen.  UV–Vis spectra. Protein has evident absorption in the region of ultraviolet light. It is due to the ultraviolet phenacylmethylene groups in protein molecule. Generally, the maximum absorption wavelength of protein between 250 to 290 nm. However, there is no obvious absorption for collagen in this region. UV-Vis spectra of pepsin-soluble collagen from Amiurus nebulosus skin was shown in Fig. 7. Pepsin-soluble collagen had absorption near 234 nm. This was in agreement with those of collagens from bullfrog skin (236 nm) [33] and channel catfish skin (232 nm) [18]. Also, this result further proved that a high-purity was achieved for pepsin-soluble from Amiurus nebulosus skin.    0.600.8

e0.450.6

a0.4

br0.30A

o  s0.2

A630.710.150.00.00-0.2

2002503003504004505004000300020001000

Wavelength (nm)Wavenumber(cm-1)

Fig 7.  UV-Vis spectra of pepsin-soluble  Fig 8.  Fourier transform infrared spectrum of  collagen from Amiurus nebulosus skin. pepsin-soluble collagen of Amiurus nebulosus

skin.

Fourier transforms infrared spectra (FTIR). The Fourier transforms infrared spectroscopy of the pepsin-soluble collagen from the skin of Amiurus nebulosus was represented in Fig.8. It was similar to that of other species collagens [31-32]. Generally, a free N-H stretching vibration occurs in the range of 3400–3440 cm-1. When the NH group of a peptide is involved in a hydrogen bond, the position is shifted to lower frequency, usually 3300 cm-1

-1[33]. The amide A band position was found at 3298.22 cm, which was the absorption band of N-H stretching. It showed that there were hydrogen bonds presented in pepsin-soluble collagen. Amide B band was found at 3080.26 cm-1, where the amide B band of collagen always appears [34].The spectra of the pepsin-soluble collagen dispersions also demonstrated the characteristic pattern reflecting the amide I band at 1668.40 cm-1, the amide II band at 1539.17 cm-1, and the amide III band at 8.28 cm-1, resulting from C=O-stretching, N=H-bending vibrations and C=H-stretching [35], respectively. The amide I band which is associated with the secondary structure of the protein and the amide III band proved the existence of helical structure [19-20, 36]. Thus, the FTIR investigations indicated the existence of helical arrangements of skin collagen of Amiurus nebulosus.

Denaturation temperature. Fig.9 showed fractional viscosity for pepsin-soluble collagen of Amiurus nebulosus skin. The viscosity

of collagens reduced greatly with temperature. The denaturation temperature (Td) of the collagens was taken to be the temperature at which the fractional viscosity was 0.5. Td of the skin collagen of Amiurus nebulosus was about 22.0℃ that was lower by about 15℃ than that of porcine skin collagen (37.0℃). It was also lower than many cold-water fish, such as Japanese seabass (26.5℃) [6], chub mackerel (25.6℃), bullhead shark (25 ℃), Ocellate puffer fish (28℃) [5] , paper nautilus (27℃) [5], rhizostomous jellyfish (28.8℃) [6]. These observations were attributed to the high amino acid content and high degree of hydroxylation of proline. Hydroxyproline is important in maintaining the stabilization of the trimmers in collagen. It is

known that the stability of collagen is correlated with environmental and body temperature [27]. This result well supported these findings.

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em(gp4

naU

ho

cd3

lnaE n

owo2i

tcl

aF

rt

F1

ea

00153045607590

Temperature(℃)

Fig 9.  Thermal denaturation curve of  Temperature(℃)

Fig 10.  Thermal transition curve of

pepsin-soluble collagen solution was measured pepsin-soluble collagen (PSC) from Amiurus by viscosity in 0.5 M acetic acid. The incubation nebulosus skin, as shown by DSC. time at each temperature was 10 min, and the

collagen concentration was 0.5 mg/ml.

Differential scanning calorimetric (DSC). Thermal stability of collagen is usually described by the denaturation temperature (Td) in solution and the shrinkage temperature (Ts) of fiber. The temperature at which the triple helix structure of collagen is disintegrated into random coils is considered as Td [37]. The shrinkage temperature refers to the temperature at which collagen fiber shrinks to one third of its length [38]. During the shrinkage process, a phase transition involves the conversion of a crystalline triple helical collagen structure to an amorphous random coil form [39]. Ts of pepsin-soluble collagen from Amiurus nebulosus skin was found to be at 66.63℃(Fig.10), about 4℃ higher than that of type І collagen from bovine skin (62.0℃) and higher than that of PSC from the body wall of sea cucumber (57.0

℃) [16]. The thermal stability is influenced by the imido acid content, the higher the imido acid content, the more stable the helices, for the molecular structure of collagen is maintained mainly by restrictions on changes in the secondary structure of the polypeptide chain (imposed by the pyrrolidine rings of proline and hydroxyproline), and also maintained partially by the hydrogen bond ability through the hydroxyl group of hydroxyproline [31]. On the other hand, the stability of collagen is also known to be correlated with the environmental and body temperatures

[27].

Conclusion

Pepsin-soluble collagen extracted from Amiurus nebulosus skin with a high yield of 97.44% was classified as type I collagen. It had a distinct amino acid position and thermal stability, different from those of bovine or porcine skin collagens. The transition temperature or denaturation temperature of the collagen from Amiurus nebulosus skin was lower than those of collagens from mammals. FTIR investigations showed the existence of helical arrangements of collagen. Thus, Amiurus nebulosus skin was a good source of collagen. This study provided a theoretical basis for collagen modification and utilization. However, Amiurus nebulosus collagen may need further modification or purification in some fields.

Acknowledgments

We are grateful for financial support from the Research Grants Committee of 948 (Project No.2010-Z57).

References

[1] J.H. Muyonga, C.G.B. Cole, K.G. Duodu: Food Chemistry, Vol. 85 (2004), p. 81

[2] P. Kittiphattanabawon, S. Benjakul, W. Visesanguan, T. Nagai, M. Tanaka: Food Chemistry, Vol.

89 (2005), p. 363

[3] M.C. Gomez-Guillen, J. Turnay, M.D. Fernandez-Diaz, N. Ulmo, M.A. Lizarbe, P. Montero: Food Hydrocolloids, Vol. 16 (2002), p. 25

[4] I.E. Koladziejaka, Z. Silorski, C. Niecikowska: Food Chemistry, Vol. 66 (1999), p. 153

[5] Nagai, Takeshi, Araki, Yoko, Suki: Food Chemistry, Vol. 78 (2002), p. 137

[6] Nagai, Takeshi, Suki, Nobutaka: Food Chemistry, Vol. 68 (2000), p. 277

[7] M. Ogawa, R.J. Portier, M.W. Moody, J. Bell, M.A. Schexnayder, J. N.  Losso: Food Chemistry,

Vol. 88 (2004), p. 495

[8] M. Sadowska, I. Koladziejaka, C. Niecikowska: Food Chemistry, Vol. 81 (2003), p. 257

[9] A. Jongjareonrak, S. Benjakul, W. Visessanguan, T. Nagai, M. Tanaka: Food Chemistry, Vol. 93 (2005), p. 475

[10] P. Montero, M.C. Go´mez-Guille´n, A.J. Borderias: Food Chemistry, Vol. 65 (1999), p. 55

[11] S. Morimura, H Nagata, Y. Uemura, A. Fahmi, T.  Shigematsu, K.  Kida: Process Biochemistry,

Vol. 37 (2002), p. 1403

[12] K. Yoshimura, M. Terashima, D. Hozan, K. Shirai: Journal of Agriculture and Food Chemistry,

Vol. 48 (2000), p. 685

[13] Anonymous. Meat and meat products-determination of L (-) hydroxyproline content (reference

method) (International Standard, ISO 3496(E) 1978)

[14] U.K. Laemmli: Nature, Vol. 227 (1970), p. 680

[15] S. Kimura, X. Zhu, R. Matsui, M. Shijoh, S. Takamizawa: Journal of Food Science, Vol. 23

(1988), p. 1315

[16] F.X. Cui, C.H. Xue, Z.J.  Li, Y.Q. Zhang, P. Dong, X. Y. Fu: Food Chemistry, Vol. 100 (2007),

p. 1120

[17] P. Sivakumar, R. Arichandran, L. Suguna, M. Mariappan,  G. Chandrakasan: Journal of Fish

Biology, Vol. 56 (2000), p. 999

[18] H.Y. Liu, D. Li, S.D. Guo: Food Chemistry, Vol. 101 (2007), p. 621

[19] J.H. Muyonga, C.G.B. Cole, K.G. Duodu: Food Chemistry, Vol. 85 (2004a), p. 81

[20] J.H. Muyonga, C.G.B. Cole, K.G. Duodu: Food Chemistry, Vol. 86 (2004b), p. 325

[21] G. Balian, J.H. Bowes, The structure and properties of collagen. The science and technology of

gelatin. London: Academic Press. (1977), p. 1

[22] S. Grossman, M. Bergman: US Patent 5,093,474. (1992)

[23] M. Gudmundsson, H. Hafsteinsson: Journal of Food Science, Vol. 62 (1997), p. 37

[24] C. Yoshida, S. Fujisawa, S. Mita, R. Yoshinaka: Journal of Food Science, Vol. 66 (2001), p.

247

[25] P.M.  Gilsenan, S.B. Ross-Murphy: Food Hydrocolloids, Vol. 14 (2000), p. 191

[26] R.E. Norland, Fish Gelatin. In M. N. Voight, J.K. Botta (Eds.), Advances in fisheries technology

and biotechnology for increased profitability. Lancaster, PA: Technomic Publishing. (1990), p. 325

[27] B.J. Rigby: Nature, Vol. 219 (1968), p. 166

[28] M.C. Go` mez-Guille`n, J. Turnay, M.D. Ferna′ndez-Diaz, N. Ulmo, M.A. Lizarbe, P. Montero:

Food Hydrocolloids, Vol. 16 (2002), p. 25

[29] T. Nagai, E. Yamashita, K. Taniguchi, N. Kanamori, N. Suki: Food Chemistry, Vol. 72 (2001),

p. 425

[30] A.J. Bailey, N.D. Light: Connective tissue in meat and meat products (New York: Elsevier

Applied Science 1989).

[31] Y. Zhang, W.T. Liu, G.Y. Li, B. Shi, Y.Q. Miao, X.H. Wu: Food Chemistry, Vol. 103 (2007), p.

906

[32] J.H. Muyonga, C.C.G.B. Cole, K.G. Duodu: Food Chemistry, Vol. 86 (2004), p. 325

[33] A. Kaminska, A. Sionkowska: Polymer Degradation and Stability, Vol. 51 (1996), p. 19

[34] H. Li, B.L. Liu, L.Z. Gao, H.L. Chen: Food Chemistry, Vol. 84 (2004), p. 65

[35] K.J. Payne, A. Veis: Biopolymers, Vol. 27 (1988), p. 1749

[36] W.K. Surewicz, H.H. Mantsch: Biochimicaet Biophysica Acta, Vol. 952 (1988), p. 115

[37] L.H. Hao, B.F. Li: J. Fish. Sci. Chin. Vol. 6 (1999), p. 18

[38] N.N. Fathima, B. Madhan, J.R. Rao, B.U. Nair, T. Ramasami: Int. J. Biol. Macromol. Vol. 3

(2004)4, p. 241

[39] N. Fathima, N.M. Balaraman, J.R. Rao, B.U. Nair: J. Inorg. Biochem. Vol. 95 (2003), p.47

Application of Chemical Engineering

doi:10.4028/.scientific.net/AMR.236-238

Extraction and Partial Characterization of Pepsin-Soluble Collagens from the Skin ofAmiurus Nebulosus

doi:10.4028/.scientific.net/AMR.236-238.2926

作文二:《关于长沙市民对长沙房价的调查报告》1700字

关于长沙市民对长沙房价的调查报告

班级:557班   姓名:XXX  学号:10015750849

一、调查时间:2012年6月9日晚

二、调查地点:长沙市河西沿江风光带

三、访谈对象:长沙市民刘先生、贺小姐、张先生(专业人士)

四、访谈记录:

周六晚与同学相约湘江边上看烟花,并利用这个机会随机采访了三位市民,请他谈谈对如今长沙房价的看法。现将此次访谈记录如下:

第一位接受采访的是市民刘先生。刘先生是长沙本地人,三十多岁,在麓谷某家药品公司上班,收入不是特高但也还算稳定。

谈起自己的购房经历,他说,自己于两年前在岳麓区湘麓国际小区购买了一套三室两厅的房子,但由于儿子在桐梓坡小学读书,考虑到儿子学习的不方便,一家四口便在桐梓坡英才园小区又租了一套房子。“当时买的那套房是4千多一平米,相对现在来说还是比较实惠的。”刘先生介绍说。对于现今日益增长的房价,他表示,就他个人而言,价格还是购房选择的首要因素,其次是工程质量和地理位置。同时,自己当时资金有限,只付得起首付,所以购房资金的主要来源是银行贷款,虽然每个月要还房贷,压力比较大,但他还是为自己感到庆幸。“还好当时一咬牙买下来了,现在购房压力更大,像普通上班族每个月工资也就两千左右,房价又那么不稳定,涨得飞快,买个一百平米的小户型都要五六十万,得奋斗多少年啊!”

说到现在的购房现状,他建议,消费者还是应该理性对待,其实房价一直是起起落落的,大家可以持观望态度。同时,一定要从多方面考虑,多进行比较,例如,交通配套等方面。 准备把父母接来同住的贺小姐心情很好,她说道:存折里的数字正在上升,筹划已久的买一套三房的计划终于可以开始实施了。两个月后,贺小姐的存款虽然没有下降,但是买房的计划却搁浅了。“之前问过的几个盘,单价都从4000元左右涨到了5000元左右,价格便宜一点的,不是到了星沙就是到了暮云,我不知道这是为什么?房价这样涨,我已经很难承受了。”

不仅是疯涨的房价,而是原以为可以在这个城市过得更好的自信心,正在消退。在这个城市里打拼了近十年,和老公都算得上公司中层管理人员,他们的职业和收入都一度是周围的同事朋友们羡慕的对象,怎么到了买房子的时候,辛苦十年的小小成就感,怎么一下子就被击得粉碎了。“房价如果一直涨,我还能买得起吗?当房价涨幅开始质疑我们生存的能力,对这个城市我有点爱不起来了。”

第三位张先生说道:长沙作为一个内地身份的省会,其房价在全国同等城市里并不显得过高;和沿海规模差不多的城市及内地一些被过度炒作的城市比较;还不算很离谱;所以最近关于长沙房价应该“补涨”的说法被很多人接受,即使本地老百姓也认为在长沙投资房产是很稳当的事情,我很多朋友就买了好几套房,哪怕其他的开支都砍掉也要买房子,认为这个是不会亏的,有时候去新楼盘看看的时候,到处都是江浙口音的顾客在看房。好像长沙的房子真的还有很大的升值空间一样,真是这样的吗?我看不见得。

长沙只是一个内地的中等城市,吸引外地具名来定居的能力取决于它能提供的工作机会是否具备良好的人居环境,就是长沙提供工作机会的能力而言,除非有天才的运作大师,否则长沙的工商业水平很难短期内形成很大的就业空间,人居环境的话,也不是一朝一夕能有很大的进步的,至少现在看来没有多少比周边城市很具有优势的地方,所以长沙房地产的发展很大程度取决于湖南本省的城市化速度,基本上应该是本地工作有住房需要的人群和少数下面地县富裕起来了有需要到长沙人群。

那么现在的房子为什么还是这么好卖呢?是谁卖了呢?答案是:炒家,专业的炒家和业余的炒家,外地炒家觉得长沙房子还可以炒,本地人再没什么投资渠道的情况下,也跟着炒,问题是房子不是拿来吃的,总要能转手或者出租才有用的啊,现在长沙房子的存量已经够长沙发展到2020年用了,还这么拼命炒下去有意义不?

所以我的看法是:房价会回到理性,也就是价格会回到成本上下,长沙现在小高层的建安成本一般在600-900元/M2,加上土地费用,早几年哪的地摊下来不超过200元/M2(指周边地区),如果房价理性上涨,开发商不这么疯狂的话,这样的成本,销售价格应该在1500-2000元/平方米上下,但考虑到现在长沙的房子应经远远供大于求,一旦房价开始跌,低于成本销售也是有可能的,呵呵。

不过这也只是我对于房价的个人看法,毕竟掌握的资料有限,只是大概估计,还是希望大家在买房的时候要有自己的判断。

作文三:《关于“长沙名吃”的内容》2300字

关于“ 吃” 关名于“长沙名 吃”内的容

址地:一线新环开铺教劳所对面 荐菜推:味合腊,蒸竹烧肉,腐豆烧土,炒肉味 腊腊味合,蒸腐烧肉竹,土豆烧肉

,店 :名

蒋记腊禽馆 花江狗肉,

花江肉,腊狗回锅味

地:址 郊公园对南面推 菜荐:

名:易 记粉店 晚上卖味口虾 易记粉(店晚上卖味虾口晚上 口卖味虾 ) 地:址长沙白沙路城南和路界交的桥面往碧水蓝天下方向推 荐:口菜味虾(大很只而且一是块一钱一)只 口味

店虾名:喜 相韩国烧烤 地逢 址:沙金长年色旁华的三边街兴

踏板

鱼牛, 肉韩国面,冷推 菜荐:踏鱼 板肉牛,韩国面冷,石拌锅饭 板鱼 牛肉踏韩国 冷面

店 名:猫河记馆鱼猫记 鱼河馆  址:地湘江边的湘潇大湖道大牌口 楼推菜荐:种各河鱼白鸭叫  黄鸭 桂鱼叫 各河种鱼白鸭叫 黄鸭,叫桂,鱼 鸭白,叫黄鸭叫

:童名水鱼馆仔 地 :万家丽路雨址花区政对面

仔童鱼(水味口法做 口蛇,宁味鱼翅乡推 荐:菜童仔水鱼 味做口,法卤 水味蛇 宁口乡翅鱼童 水仔鱼口味做法, 卤水,)味口

店蛇名 天利:味口排挡大地  :址江大道营沿街交界处盘推荐 菜:味口(蛇82 口蛇(味

元斤) 口

蟹味元 )斤,味口

店 :名虾潭口大味排挡1

:香址路椿营盘街交界道处 荐推:干口菜味虾

店名明盛 :盛 地明 址:南街往洋三角花方园向 推菜:荐辣炒椒肉,怪味鸡,撕包菜,手寒排菌汤 辣椒骨肉,炒怪鸡味手撕包菜,寒,排骨菌

店 名:何氏排汤 地 骨:人民址路鼓花团剧隔 推荐菜壁霸王:排 霸骨王骨

名店:肚牛 地王址 雨:花区公安局面 推荐对菜牛肚

店 名:许:记蛙牛 地 :劳址动西沿江路光风带界交(新店处) 冬,瓜解山四村 6放10终点站 老()店 推荐:菜干锅蛙牛口,牛味,辣蛙椒蚌壳炒 干肉牛蛙, 锅干牛锅蛙口味牛蛙,

:名杜鸡 家地 址银:路何银盆湾路界交 推处荐:菜杜家

店名:

031 家7馆菜

地:河西潇湘址道和大民路新交处界推 菜荐岳:母娘味鸡口 母岳口味娘鸡

店名: 胡兵小鹅馆肉 胡小兵鹅馆 地肉址 :士公园烈门南岛上咖啡旁边居的民内区 推菜:荐锅干鹅肉干 2

名:河西店猪王脚地 址:芙蓉南路社会 福利院 推荐菜旁猪:脚

店名:

红灯区

址:岳 麓山山半 推腰菜荐:酸炒菜 肉酸炒菜肉

店:周大福汤名 地 店:址湾渔市天公寓门马口

肚片莲子汤, 推菜:荐片肚莲汤子,鸽乳汤店

名:毛 子 坨地 :址南口长郡中学巷内

门各色凉菜,糖排骨,醋推 菜荐:各色凉,糖醋菜排,骨干

粉店 名建军蒸:馆菜建军蒸 菜馆地  :址大一路华远天东紫旁阁 推边菜荐:川豆菜,酸腊牛肉川 豆酸,菜

店名

净:果甜

地址 韶:山路景名鸿厦楼(瑶岭)一

豆红布丁,芒雪果

糕西米, 捞荐推:红菜豆丁布,芒雪糕西米果捞芒椰,粒粒

店爽 :名弟兄家 之 地:树木址岭推荐 :菜辣椒肉 小炒牛肉 辣椒炒炒肉小炒,牛

肉蒸蛋

店名巴乡居:3

地址:

170 道过大托机国 20场 米左0右开车的话走完芙。南路右转蓉约 05 0米

寿福螺,乡巴,鱼 推菜荐:福螺寿巴,鱼乡,牛粉丝

肉名:店第一家(酒老八路 )第一酒(老八家)路地 :址长沙东塘信举旁巷电内推荐菜: 辣鱼,香草鸭 香稻辣鱼

,店

:名菜看下饭地 :址人民路锷蔡路界处 推荐菜:交开胃猪 红脚烧珍珠豆土 香辣肠肥 开胃猪铂,红烧脚珠土豆珍红 烧珍土珠,香豆辣肥肠

铂海民渔(宁波村菜 )店:民海渔名(村宁菜)

地波:雅址村塘路一吉对祥 推面荐:凉菜鲨鱼拌,福皮建丸 鱼凉拌鱼皮鲨,

家乡土菜安馆。店 名东安家:土菜乡。

馆址地燕山街:面里协宾馆湘面对 荐菜:推东安(很正鸡的宗嘿嘿。我,是安东人最喜,欢这个)吃

名店:人人家地 址:前在林以门口校,现在据说搬去星大市场那红边: 了 推荐菜(村:鱼姑青,椒肉炒,香。干 村姑鱼青,椒肉,炒干香

店名:林湘大酒店 地址:广济桥林厅业待所招推 荐:菜椒炒水青鱼铁板,肉蛋牛青 椒水炒,

店名郑:记黄金台猪老脚店 地址:字领下识沙白路 荐菜推:脚

店名:沙老爹口味虾 城地:址八一桥路段 荐推菜:爆干 口虾蟹 味香菜菇 心干虾爆口,蟹 味味蟹口香,菇心菜店名 海:一条鲜 巷址:西地路,湖长中郡学斜面建对建行设旁边推 菜:荐老妈圣干皇(那子里的海鲜很都宜便,)味口蛇1  0/斤元

:名南昌表老 地:晓址园路丽写真瑞隔壁推荐菜: 类煲各汤(盅卖按)的

:浏名蒸阳菜 址地蔡:谔大令婚纱对路 门推菜:手荐鱼

撕名:店猫夜 地子:火星址霄路凌火小学对面星 推荐:坛菜汤菜子

名店:烧 地址:烤对湖河大南院推荐 :火鸡翅膀

菜店名:永血州鸭 地馆:址蓉芙老树路啡旁边咖那楼栋的楼七,永长沙州办处事 推菜荐永州血:

鸭店

名:福土菜天

馆5

址:车地北站路王府花园边旁的巷子里

面味口蟹大,蒜炒牛腊肉 丝粉白,芽尖椒肠大 蒜大炒腊肉,牛粉丝白 推荐芽:口菜蟹 大蒜炒味牛肉 粉丝腊白芽 椒大尖

肠名:店三腊味馆 姐址地浏阳:边*近河金帆区小高尔和球场的夫地 推荐方:菜有腊所味

名杨胖子卤味: 地店:址子坡*近河街的边地 方推菜:四合荐一意随搭配建一议定放韭菜要

名店:

记蜗富店牛干 锅牛,蜗口虾 干味蜗锅牛 口味

地址 :花池旁荷边学路工巷子的里 推荐:

菜店

名:

记凉面 邹馄,凉饨,粉血猪,汤卜萝炖骨头,海带炖骨头 馄,饨凉粉,猪血,汤萝,卜炖骨头,海

带炖骨头,瓜炖骨冬头

地址: 南门

老树口咖对啡一条巷子里门,又小叫雨平厂 荐推:菜

:名

岭上人家 黄瓜煮蟮、手鱼撕捆鸡小炒、牛腊、蒸肉肉、拌刀豆腊 黄、瓜蟮鱼、煮撕捆手鸡小炒腊、肉牛、腊肉蒸拌、豆刀、炒油

址 :白沙路南 荐菜:

菜苔、 菜、酸菜苔炒苦瓜好再 来香 辣、鱼煸四季豆干、铁牛肉板、清韭炒菜、豆腐汤脑 、香辣鱼、煸干四豆、铁季板肉牛清炒、韭菜、腐豆汤、香

店:名

址 春天:货西百边小 巷推荐:

土辣片豆 、辣土片、豆猪熘