利用蛋白質體學方法分析史特拉底瓦里小提琴上的古代膠

Abstract

安東尼奧．史特拉底瓦里是史上公認最好的弦樂器工匠，幾乎所有的小提琴演奏者都夢想擁有一把史特拉底瓦里小提琴，使得這些珍貴的古董樂器的拍賣價格居高不下，也讓世上所有的製琴師嘔心瀝血地嘗試重製出一樣的名琴，至今卻沒有任何人成功。在一把1725年製造的史特拉底瓦里小提琴的琴頸中，我們發現了一塊用來黏木頭的膠。雖然此小提琴膠並不是由安東尼奧·史特拉底瓦里本人使用，但仍然是一個珍貴的樣品，可以用來了解兩百多年前的製琴師偏好使用何種小提琴膠。 在本研究中，利用蛋白質體學的方法，先以胰蛋白脢將小提琴膠分解成胜肽，再利用液態層析串聯質譜及軟體Mascot進行後續分析。我們成功地鑑定這塊來自名琴的古董膠的主成分為純度很高的膠原蛋白，和美國國家生物技術資訊中心的資料庫進一步的比對後，我們推斷這些膠原蛋白最有可能來自於牛。然而由於基因同源性的影響，並不能完全排除在演化過程中和牛親屬關係很近的綿羊和山羊的可能性。現代的製琴師仍會在製造小提琴時使用主要成分為牛皮的皮革膠(hide glue)，代表兩百年來製琴界在膠的選擇上並沒有太大的改變。本研究也證明我們設計的新蛋白質體學分析方法能夠分析蛋白質膠並鑑定其成份及物種來源。

Antique violins made in Cremona, Italy by Antonio Stradivari (1644-1737) have superlative qualities, especially their tonal and visual beauty. Many luthiers have tried to unravel their mysteries over past three centuries. Violin makers and researchers are still trying to understand what materials were used to construct these highly valuable instruments. During violin making, protein-based glues are used to join different pieces of wood together. Some have proposed that Stradivari used casein (cheese) glue instead of common collagen glues for certain joints. During our research into wood treatment of a Stradivari violin which made in 1725, we accidentally encountered a piece of glue used for neck modification dating back to about 1800 CE. Although it was not the original glue applied by Stradivari himself, it nevertheless represented the first old glue sample analyzed from an antique violin. The old glue was analyzed by direct trypsinization and liquid chromatography-mass spectrometry analysis. The proteomics data indicated the composition to be highly purified collagen without common contaminants like keratin. Further comparison with modern animal glues and genomics databases suggested that the antique sample probably originated from cow, sheep, or goat. Due to sequence homology, it is not yet possible to further differentiation between these three animal species, all from the Bovidae family. We could exclude other animal sources such as fish glue (isinglass) or rabbit glue. Today, a violin restorer would apply “hide glue” from cows for a similar repair job, and hence little has changed with respect to the choice of glues over the past 200 years. Our results demonstrate that it is possible to analyze old glue from antique violins and study its animal origin by proteomics techniques, but the mystery of Stradivari’s glue remains to be answered.